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Highlighted Publications

Pseudo-magnetic field-induced slow carrier dynamics **in periodically strained graphene, Nature Communications (2021) [arXiv: 2107.11973]**

The creation of pseudo-magnetic fields in strained graphene has emerged as a promising route to allow observing intriguing physical phenomena that would be unattainable with laboratory superconducting magnets. In this work, using time-resolved infrared pump-probe spectroscopy, we provide unambiguous evidence for slow carrier dynamics enabled by giant pseudo-magnetic fields in periodically strained graphene.

**Low-threshold optically pumped lasing in highly strained Ge nanowires, Nature Communications ‌(2017) [PDF]**

The integration of efficient, miniaturized group IV lasers into CMOS architecture holds the key to the realization of fully functional photonic-integrated circuits. In this work, we demonstrate a low-threshold, compact group IV laser that employs a germanium nanowire under a 1.6% uniaxial tensile strain as the gain medium.

All Publications

Note 1: Asterisk (*) denotes corresponding author.
Note 2: Dagger (†) denotes equal contributions.

43. H. Joo†, Y. Kim†, D. Burt, Y. Jung, M. Chen, D. Kang, L. Zhang, C. Tan, and D. Nam, ‌“1D photonic crystal direct bandgap GeSn-on-insulator laser,” Appl. Phys. Lett.*, Submitted

42. Y. Jung†, D. Burt†, Y. Kim, H. Joo, M. Chen, D. Kang, L. Zhang, C. Tan, and D. Nam, ‌“Optically pumped low-threshold microdisk lasers in GeSn-on-insulator with reduced defect density,” Appl. Phys. Lett.,* Submitted

41. D. Burt†, H. Joo†, Y. Kim, Y. Jung, M. Chen, M. Luo, S. Parluhutan, D. Kang, Z. Lin, C. Tan, Z. Ikonic, Y. Huang, and D. Nam, ‌“Direct bandgap GeSn nanowires with customized ultrahigh tension enabled in compressive-strained GeSn thin films,” Nature Commun.*, Submitted

40. M. Luo†, H. Sun†, Z. Qi, D. Kang, Y. Kim, D. Burt, M. Chen, Q. Wang, and D. Nam, ‌“Triaxially strained suspended graphene for large-area uniform pseudo-magnetic fields," Appl. Phys. Lett.*, Submitted

39. Y. Kim†, S. Assali†, D. Burt, Y. Jung, H. Joo, M. Chen, D. Kang,‌ Z. Ikonic, O. Moutanabbir* and D. Nam, “Enhanced GeSn microdisk lasers directly released on Si," Adv. Opt. Mater.*, Under Review [arXiv: 2106.00874]

38. D. Burt†, H. Joo†, Y. Jung, Y. Kim, M. Chen, Y. Huang, and D. Nam, ‌“Strain-relaxed GeSn-on-insulator (GeSnOI) microdisks,” Opt. Express*, Under Review

37. X. Gao†, H. Sun†, Q. Wang, and D. Nam, “Dynamically tunable moiré superlattice via heterostrain engineering,” Nanoscale*, Under Review

36. C. Qimiao, W. Shaoteng, Z. Lin, Z. Hao, D. Burt, D. Nam, W. Fan, and C. Tan, “GeSn-on-insulator dual-waveband resonant-cavity-enhanced photodetectors at the 2 μm and 1.55 μm optical communication bands,” Opt. Lett., Accepted (2021)

35. D. Kang†, H. Sun†, M. Luo†, K. Lu, M. Chen, Y. Kim, Y. Jung, X. Gao, S. Parluhutan, J. Ge, S. Koh, D. Giovanni, T. Sum, Q. Wang, H. Li, and D. Nam, “Pseudo-magnetic field-induced slow carrier dynamics in periodically strained graphene,” Nature* Commun., Accepted (2021) [arXiv: 2107.11973]

34. J. Ge†, B. Ding†, S. Hou†, M. Luo, D. Nam, H. Duan, H. Gao, Y. Lam, and H. Li, “Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting,” Nature Commun. 12, 3146 (2021) [PDF]

33. O. Moutanabbir, S. Assali, X. Gong, E. O'Reilly, C. Broderick, B. Marzban, J. Witzens, W. Du, S. Yu, A. Chelnokov, D. Buca, and D. Nam, “Monolithic infrared silicon photonics: The rise of (Si)GeSn semiconductors,” Appl. Phys. Lett.* 29, 118, 110502 (2021) [PDF]

32. Y. Jung†, Y. Kim†, D. Burt, H. Joo, D. Kang, M. Luo, M. Chen, L. Zhang, C. Tan, and D. Nam, “Biaxially strained germanium crossbeam with high-quality optical cavity for on-chip laser applications,” Opt. Express* 29, 14174-14181 (2021) [PDF]

31. H. Sun, P. Sengupta, D. Nam, and B. Yang, “Negative thermal Hall conductance in two-dimer Shastry-Sutherland model with π-flux Dirac triplon,” Phys. Rev. B 103, L140404 (2021) [PDF]

30. H. Sun, Z. Qi, Y. Kim, M. Luo, B. Yang, and D. Nam, “Frequency-tunable terahertz graphene laser enabled by pseudomagnetic fields in strain-engineered graphene,” Opt. Express* 29, 1892-1902 (2021) [PDF]

29. A. Dubrovkin, B. Qiang, T. Salim, D. Nam, N. Zheludev, and Q.Wang, “Resonant nanostructures for highly confined and ultra-sensitive surface phonon polaritons,” Nature* Commun. 11, 1863 (2020) [PDF]

28. Z. Song, W. Fan, C. Tan, Q. Wang, D. Nam, Z. Hua, and G. Sun, “Band structure of strained Ge1-xSnx alloy: a full-zone 30-band k·p model,” IEEE J. Quantum Electron.* 56(1), 1-8 (2019) [PDF]

27. Z. Song, W. Fan, C. Tan, Q. Wang, D. Nam, Z. Hua, and G. Sun, “Band structure of Ge1-xSnx alloy: a full-zone 30-band k·p model,” New J. Phys.* 21, 073037 (2019) [PDF]

26. H. Joo, M. Shin, H. Jung, H. Cha, D. Nam, and H. Kwon, “Oxide thin-film transistor-based vertically stacked complementary inverter for logic and photo-sensor operations,” Materials* 12(23), 3815 (2019) [PDF]

25. Z. Qi, H. Sun, M. Luo, Y. Jung, and D. Nam, "Strained germanium nanowire optoelectronic devices for photonic-integrated circuits," J. Phys. Condens. Matter.* 30(33), 334004 (2018) [PDF]

24. S. Gupta, D. Nam, J. Vuckovic and K. Saraswat, "Room temperature lasing unraveled by a strong resonance between gain and parasitic absorption in uniaxially strained germanium," Phys. Rev. B* 97(15), 155127 (2018) [PDF]

23. S. Bao†, D. Kim†, C. Onwukaeme†, S. Gupta†, K. Saraswat, K. Lee, Y. Kim, D. Min, Y. Jung, H. Qiu, H. Wang, E. A. Fitzgerald, C. Tan* and D. Nam, "Low-threshold optically pumped lasing in highly strained Ge nanowires," Nature* Commun. 8(1), 1845 (2017) [PDF]
***Featured in* LaserFocusWorld, Channel NewsAsia, *etc.***

22. D. Kim, S. Bao, C. Tan, J. Nam, K. Saraswat and D. Nam, “[Invited] The effect of germanium/silicon interface on germanium photonics,” ECS Transactions* 75(8), 683-688 (2016) [PDF]

21. D. Sukhdeo†, Y. Kim†, K. Saraswat, B. Dutt and D. Nam, “Theoretical modeling for the interaction of tin alloying with n-type doping and tensile strain for GeSn lasers,” IEEE Electron Device Lett.* 37(10), 1307-1310 (2016) [PDF]

20. J. Baek, B. Ki, D. Kim, C. Lee, D. Nam, Y. Cho, and J. Oh, “Phosphorus implantation into in-situ doped Ge-on-Si for high light-emitting efficiency,” Opt. Mater. Express* 6(9), 2939-2946 (2016) [PDF]

19. D. Sukhdeo†, Y. Kim†, S. Gupta, K. Saraswat, B. Dutt and D. Nam, “Anomalous threshold reduction from uniaxial strain for a low-threshold Ge laser,” Opt. Comm.* 379, 32-35 (2016) [PDF]

18. J. Petykiewicz†, D. Nam†, D. Sukhdeo, S. Gupta, S. Buckley, A. Piggott, J. Vučković* and K. Saraswat, “Direct bandgap light emission from strained Ge nanowire coupled with high-Q optical cavities,” Nano Lett. 16(4), 2168-2173 (2016) [PDF]
Featured in Dong-A Ilbo, Digital Times, Newsis, Asia Today*, etc.

17. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam, “Impact of minority carrier lifetime on the performance of strained Ge light sources,” Opt. Comm.* 364, 233-237 (2016) [PDF]

16. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam, “Ultimate limit of biaxial tensile strain and n-type doping for realizing an efficient low-threshold Ge laser,” Jpn. J. Appl. Phys.* 55(2), 024301 (2016) [PDF]

15. D. Sukhdeo, J. Petykiewicz, S. Gupta, D. Kim, S. Woo, Y. Kim, J. Vučković, K. Saraswat and D. Nam, “Ge microdisk with lithographically-tunable strain using CMOS-compatible process,” Opt. Express* 23(26), 33249-33254 (2015) [PDF]

14. Y. Kim, J. Petykiewicz, S. Gupta, J. Vučković, K. Saraswat, and D. Nam, “Strained Ge light emitter with Ge on dual insulators for improved thermal conduction and optical insulation,” IEIE SPC* 4(5), 318-323 (2015) [PDF]

13. D. Sukhdeo, D. Nam, J. Kang, M. Brongersma and K. Saraswat, “Bandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics,” Opt. Express* 23(13), 16740-16749 (2015) [PDF]

12. J. Nam, F. Afshinmanesh, D. Nam, W. Jung, T. Kamins, M. Brongersma, and K. Saraswat, “Monolithic integration of germanium-on-insulator p-i-n photodetector on silicon,” Opt. Express* 23(12), 15816-15823 (2015) [PDF]

11. J. Nam, S. Alkis, D. Nam, F. Afshinmanesh, J. Shim, J. Park, M. Brongersma, A. Okyay, T. Kamins and K. Saraswat, “Lateral overgrowth for monolithic integration of germanium-on-insulator on silicon,” J. Cryst. Growth* 416, 21-27 (2015) [PDF]

10. D. Nam, J. Kang, M. Brongersma and K. Saraswat, “Observation of improved minority carrier lifetimes in high-quality Ge-on-insulator using time-resolved photoluminescence,” Opt. Lett.* 39(21), 6205-6208 (2014) [PDF]

9. D. Nam, D. Sukhdeo, B. Dutt and K. Saraswat, “[Invited] Light emission from highly-strained germanium for on-chip optical interconnects,” ECS Transactions* 64(6), 371-381 (2014) [PDF]

8. D. Nam, D. Sukhdeo, S. Gupta, J. Kang, M. Brongersma and K. Saraswat, “Study of carrier statistics in uniaxially strained Ge for a low-threshold Ge laser,” IEEE J. Sel. Top. Quant. Electron. 20(4), 16-22 (2014) [PDF]

7. D. Sukhdeo, D. Nam, J. Kang, M. Brongersma and K. Saraswat, “[Invited] Direct bandgap germanium-on-silicon inferred from 5.7% uniaxial tensile strain,” Photonics Research* 2(3), A8-A13 (2014) [PDF]
Highlights: Selected as #1 most cited paper during 2014-2015

6. B. Dutt, H. Lin, D. Sukhdeo, B. Vulovic, S. Gupta, D. Nam, K. Saraswat, and J. Harris, “theoretical analysis of GeSn alloys as a gain medium for a Si-compatible laser,” IEEE J. Sel. Top. Quant. Electron. 19(5), 1502706 (2013) [PDF]

5. D. Nam, D. Sukhdeo, J. Kang, J. Petykiewicz, J. Lee, W. Jung, J. Vuckovic, M. Brongersma, and K. Saraswat, “Strain-induced pseudoheterostructure nanowires confining carriers at room temperature with nanoscale-tunable band profiles,” Nano Lett. 13(7), 3118-3123 (2013) [PDF]

4. B. Dutt, D. Sukhdeo, D. Nam, B. Vulovic, Z. Yuan, and K. Saraswat, “Roadmap to an efficient germanium-on-silicon laser: strain vs. n-type doping,” IEEE Photon. J.* 4(5), 2002-2009 (2012) [PDF]

3. W. Jung, J. Park, A. Nainani, D. Nam, and K. Saraswat, “Fluorine passivation of vacancy defects in bulk Ge metal-oxide-semiconductor field effect transistor application,” Appl. Phys. Lett. 101(7), 072104 (2012) [PDF]

2. D. Nam, D. Sukhdeo, S. Cheng, K. Huang, A. Roy, M. Brongersma, Y. Nishi, and K. Saraswat, “Electroluminescence from strained Ge membranes and implications for an efficient Si-compatible laser,” Appl. Phys. Lett. 100(13), 131112 (2012) [PDF]

1. D. Nam, D. Sukhdeo, A. Roy, K. Balram, S. Cheng, K. Huang, Z. Yuan, M. Brongersma, Y. Nishi, D. Miller and K. Saraswat, “Strained germanium thin film membrane on silicon substrate for optoelectronics,” Opt. Express* 19(27), 25866-25872 (2011) [PDF]

Patent

6. Non-Drafted Singapore Patent Application: “Biaxially strained crossbeam germanium laser structure,” D. Nam, D. Burt, Y. Jung, Y. Kim, H. Joo, Submitted on 16 Dec 2020

5. Non-Drafted Singapore Patent Application: “Graphene nanopillar structures for giant pseudo-magnetic fields,” D. Nam, D. Kang, M. Luo, H. Sun, X. Gao, K. Lu, Submitted on 15 Dec 2020

4. Non-Drafted Singapore Patent Application: “Triaxially strained graphene structure for large-area pseudo-magnetic field,” D. Nam, H. Sun, M. Luo, D. Burt, D. Kang, Submitted on 14 Dec 2020

3. Non-Drafted Singapore Patent Application, Application Number 10202012548S: “An electrically pumped strained GeSn laser structure,” D. Nam, D. Burt, Y. Jung, Y. Kim, H. Joo, Filed on 15 Dec 2020

2. Non-Drafted Singapore Patent Application, Application Number 10201806832X: “Highly strained germanium laser on a silicon platform,” D. Nam, C. Tan, Filed on 13 Aug 2018

1. US Patent No.0,372,455: “Crossed nanobeam structure for a low-threshold germanium laser,” D. Nam, J. Petykiewicz, D. Sukhdeo, S. Gupta, J. Vuckovic, K. Saraswat, Issued Sept. 9, 2015 [LINK]

Highlighted Publications

Pseudo-magnetic field-induced slow carrier dynamics in periodically strained graphene, Nature Communications (2021) [arXiv: 2107.11973]

Low-threshold optically pumped lasing in highly strained Ge nanowires, Nature Communications ‌(2017) [PDF]

All Publications

Note 1: Asterisk (*) denotes corresponding author.Note 2: Dagger (†) denotes equal contributions.

43. H. Joo†, Y. Kim†, D. Burt, Y. Jung, M. Chen, D. Kang, L. Zhang, C. Tan, and D. Nam*, ‌“1D photonic crystal direct bandgap GeSn-on-insulator laser,” Appl. Phys. Lett., Submitted

42. Y. Jung†, D. Burt†, Y. Kim, H. Joo, M. Chen, D. Kang, L. Zhang, C. Tan, and D. Nam*, ‌“Optically pumped low-threshold microdisk lasers in GeSn-on-insulator with reduced defect density,” Appl. Phys. Lett., Submitted

41. D. Burt†, H. Joo†, Y. Kim, Y. Jung, M. Chen, M. Luo, S. Parluhutan, D. Kang, Z. Lin, C. Tan, Z. Ikonic, Y. Huang, and D. Nam*, ‌“Direct bandgap GeSn nanowires with customized ultrahigh tension enabled in compressive-strained GeSn thin films,” Nature Commun., Submitted

40. M. Luo†, H. Sun†, Z. Qi, D. Kang, Y. Kim, D. Burt, M. Chen, Q. Wang, and D. Nam*, ‌“Triaxially strained suspended graphene for large-area uniform pseudo-magnetic fields," Appl. Phys. Lett., Submitted

39. Y. Kim†, S. Assali†, D. Burt, Y. Jung, H. Joo, M. Chen, D. Kang,‌ Z. Ikonic, O. Moutanabbir* and D. Nam*, “Enhanced GeSn microdisk lasers directly released on Si," Adv. Opt. Mater., Under Review [arXiv: 2106.00874]

38. D. Burt†, H. Joo†, Y. Jung, Y. Kim, M. Chen, Y. Huang, and D. Nam*, ‌“Strain-relaxed GeSn-on-insulator (GeSnOI) microdisks,” Opt. Express, Under Review

37. X. Gao†, H. Sun†, Q. Wang, and D. Nam*, “Dynamically tunable moiré superlattice via heterostrain engineering,” Nanoscale, Under Review

36. C. Qimiao, W. Shaoteng, Z. Lin, Z. Hao, D. Burt, D. Nam, W. Fan, and C. Tan, “GeSn-on-insulator dual-waveband resonant-cavity-enhanced photodetectors at the 2 μm and 1.55 μm optical communication bands,” Opt. Lett., Accepted (2021)

34. J. Ge†, B. Ding†, S. Hou†, M. Luo, D. Nam, H. Duan*, H. Gao*, Y. Lam*, and H. Li*, “Rapid fabrication of complex nanostructures using room-temperature ultrasonic nanoimprinting,” Nature Commun. 12, 3146 (2021) [PDF]

33. O. Moutanabbir*, S. Assali, X. Gong, E. O'Reilly, C. Broderick, B. Marzban, J. Witzens, W. Du, S. Yu, A. Chelnokov, D. Buca, and D. Nam, “Monolithic infrared silicon photonics: The rise of (Si)GeSn semiconductors,” Appl. Phys. Lett. 29, 118, 110502 (2021) [PDF]

32. Y. Jung†, Y. Kim†, D. Burt, H. Joo, D. Kang, M. Luo, M. Chen, L. Zhang, C. Tan, and D. Nam*, “Biaxially strained germanium crossbeam with high-quality optical cavity for on-chip laser applications,” Opt. Express 29, 14174-14181 (2021) [PDF]

31. H. Sun*, P. Sengupta*, D. Nam*, and B. Yang*, “Negative thermal Hall conductance in two-dimer Shastry-Sutherland model with π-flux Dirac triplon,” Phys. Rev. B 103, L140404 (2021) [PDF]

30. H. Sun, Z. Qi, Y. Kim, M. Luo, B. Yang, and D. Nam*, “Frequency-tunable terahertz graphene laser enabled by pseudomagnetic fields in strain-engineered graphene,” Opt. Express 29, 1892-1902 (2021) [PDF]

29. A. Dubrovkin*, B. Qiang, T. Salim, D. Nam, N. Zheludev*, and Q.Wang*, “Resonant nanostructures for highly confined and ultra-sensitive surface phonon polaritons,” Nature Commun. 11, 1863 (2020) [PDF]

28. Z. Song*, W. Fan, C. Tan, Q. Wang, D. Nam, Z. Hua, and G. Sun, “Band structure of strained Ge1-xSnx alloy: a full-zone 30-band k·p model,” IEEE J. Quantum Electron. 56(1), 1-8 (2019) [PDF]

27. Z. Song, W. Fan*, C. Tan, Q. Wang, D. Nam, Z. Hua, and G. Sun, “Band structure of Ge1-xSnx alloy: a full-zone 30-band k·p model,” New J. Phys. 21, 073037 (2019) [PDF]

26. H. Joo, M. Shin, H. Jung, H. Cha, D. Nam, and H. Kwon*, “Oxide thin-film transistor-based vertically stacked complementary inverter for logic and photo-sensor operations,” Materials 12(23), 3815 (2019) [PDF]

25. Z. Qi, H. Sun, M. Luo, Y. Jung, and D. Nam*, "Strained germanium nanowire optoelectronic devices for photonic-integrated circuits," J. Phys. Condens. Matter. 30(33), 334004 (2018) [PDF]

24. S. Gupta*, D. Nam, J. Vuckovic and K. Saraswat, "Room temperature lasing unraveled by a strong resonance between gain and parasitic absorption in uniaxially strained germanium," Phys. Rev. B 97(15), 155127 (2018) [PDF]

22. D. Kim, S. Bao, C. Tan, J. Nam, K. Saraswat and D. Nam*, “[Invited] The effect of germanium/silicon interface on germanium photonics,” ECS Transactions 75(8), 683-688 (2016) [PDF]

21. D. Sukhdeo†, Y. Kim†, K. Saraswat, B. Dutt and D. Nam*, “Theoretical modeling for the interaction of tin alloying with n-type doping and tensile strain for GeSn lasers,” IEEE Electron Device Lett. 37(10), 1307-1310 (2016) [PDF]

20. J. Baek, B. Ki, D. Kim, C. Lee, D. Nam, Y. Cho, and J. Oh*, “Phosphorus implantation into in-situ doped Ge-on-Si for high light-emitting efficiency,” Opt. Mater. Express 6(9), 2939-2946 (2016) [PDF]

19. D. Sukhdeo†, Y. Kim†, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Anomalous threshold reduction from uniaxial strain for a low-threshold Ge laser,” Opt. Comm. 379, 32-35 (2016) [PDF]

17. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Impact of minority carrier lifetime on the performance of strained Ge light sources,” Opt. Comm. 364, 233-237 (2016) [PDF]

16. D. Sukhdeo, S. Gupta, K. Saraswat, B. Dutt and D. Nam*, “Ultimate limit of biaxial tensile strain and n-type doping for realizing an efficient low-threshold Ge laser,” Jpn. J. Appl. Phys. 55(2), 024301 (2016) [PDF]

15. D. Sukhdeo, J. Petykiewicz, S. Gupta, D. Kim, S. Woo, Y. Kim, J. Vučković, K. Saraswat and D. Nam*, “Ge microdisk with lithographically-tunable strain using CMOS-compatible process,” Opt. Express 23(26), 33249-33254 (2015) [PDF]

14. Y. Kim, J. Petykiewicz, S. Gupta, J. Vučković, K. Saraswat, and D. Nam*, “Strained Ge light emitter with Ge on dual insulators for improved thermal conduction and optical insulation,” IEIE SPC 4(5), 318-323 (2015) [PDF]

13. D. Sukhdeo, D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “Bandgap-customizable germanium using lithographically determined biaxial tensile strain for silicon-compatible optoelectronics,” Opt. Express 23(13), 16740-16749 (2015) [PDF]

12. J. Nam*, F. Afshinmanesh, D. Nam, W. Jung, T. Kamins, M. Brongersma, and K. Saraswat, “Monolithic integration of germanium-on-insulator p-i-n photodetector on silicon,” Opt. Express 23(12), 15816-15823 (2015) [PDF]

11. J. Nam, S. Alkis, D. Nam, F. Afshinmanesh, J. Shim, J. Park, M. Brongersma, A. Okyay, T. Kamins and K. Saraswat*, “Lateral overgrowth for monolithic integration of germanium-on-insulator on silicon,” J. Cryst. Growth 416, 21-27 (2015) [PDF]

10. D. Nam*, J. Kang, M. Brongersma and K. Saraswat, “Observation of improved minority carrier lifetimes in high-quality Ge-on-insulator using time-resolved photoluminescence,” Opt. Lett. 39(21), 6205-6208 (2014) [PDF]

9. D. Nam, D. Sukhdeo, B. Dutt and K. Saraswat*, “[Invited] Light emission from highly-strained germanium for on-chip optical interconnects,” ECS Transactions 64(6), 371-381 (2014) [PDF]