III-Nitride Tunneling Hot Electron Transfer Amplifier (THETA)
In this chapter, we investigate vertical transistors based on hot electron transport—tunneling hot electron transfer amplifier (THETA). As compared to lateral transport devices such as HEMTs, electron transport can be defined by heterojunction growth at a scale shorter than 10 nm, and output conductance can be controlled through doping and epitaxial engineering. Furthermore, the power dissipation in a vertical device occurs over a volume rather than in a 2D sheet; the local temperature rise is not as significant as in the lateral case. THETA had been previously demonstrated in GaAs systems, and current gain in excess of 10 had been achieved with wide bandgap AlSbAs emitter at room temperature. GaN THETA has been reported in recent years, but the current gain in these devices has remained relatively low.
We demonstrate GaN THETA operating with common-emitter current gain above 10 for the first time by implementing polarization-engineered barriers in the emitter-base and base-collector junctions. Hot electron spectrometry and ballistic electron reflection in THETA were observed with the evidence of electron energy distribution and room temperature negative differential resistance (NDR). The electron-electron and coupled plasmon-phonon scatterings are key factors for the hot electron energy relaxation and broadening in base, in accordance with Monte Carlo simulation. Shrinking base thickness will reduce scattering rates and thereby increase current gain. Small signal model suggests above 200 GHz ft can be expected with a current density above 500 kA/cm2, base thickness of 5 nm and base doping of 2E20 cm2 for device mesa area less than 5 μm2.
For future work, optimizing of design to suppress output conductance and advanced processing technology to reduce parasitic components will enable highly scaled THETA for high-frequency operation.
KeywordsTunneling hot electron transistor THETA Phonon scattering Device fabrication Hot electron transport Hot electron transistor Monte Carlo simulation Polarization engineering Negative differential resistance Common-emitter current gain Gallium nitride Small signal models Vertical transistors Alloy fluctuation leakage Digital alloys Heterojunction bipolar transistor
- 15.G. Gupta et al., Common emitter operation of III-N HETs using AlGaN and InGaN polarization-dipole induced barriers. Device Research Conference (DRC), 2014 72nd Annual (2014), pp. 255–256Google Scholar
- 16.Z. Y. Digbijoy N. Nath, Pil Sung Park, and Siddharth Rajan, III-Nitride TUNNEL Injection Hot Electron Transfer Amplifier(THETA) with Common-emitter Gain. International Semiconductor Research Conference (ISDRS) (December, 2013)Google Scholar
- 17.Z. C. Yang, D. N. Nath, Y. Zhang, and S. Rajan, N-polar III-nitride tunneling hot electron transfer amplifier. Device Research Conference (DRC), 2014 72nd Annual (2014), pp. 173–174Google Scholar
- 22.L. B. R. D.K. Gaskill, K. Doverspike, Electrical transport properties of A1N, GaN and AlGaN, ed. By J. Edgar. Properties of Group III Nitrides, vol. N11, EMIS Datareviews Series (1995), pp. 101–116Google Scholar
- 23.D. N. Nath, PhD thesis (The Ohio State University, 2013)Google Scholar
- 29.J. Singh, Physics of Semiconductors and Their Heterostructures (McGraw-Hill series in electrical and computer engineering. Electronics and VLSI circuits) (McGraw-Hill, New York, 1993)Google Scholar
- 37.Z. Pei, A. Verma, J. Verma, X. Huili, P. Fay, and D. Jena, GaN heterostructure barrier diodes (HBD) with polarization-induced delta-doping. Device Research Conference (DRC), 2013 71st Annual (2013), pp. 203–204Google Scholar
- 39.M. S. William Snodgrass, and M. Feng, 150 nm InP HBT Process with Two-Level Airbridge Interconnects and MIM Capacitors for Sub-Millimeter Wave Research. presented at the CS MANTECH Conference (Tampa, Florida, USA, May 18th-21st, 2009)Google Scholar
- 40.J.W. LAI, W. HAFEZ, M. FENG, Vertical scaling of type I InP HBT with FT > 500 GHZ. 14(03), 625–631 (2004)Google Scholar
- 41.M.L. Mark Rodwell, B. Brar, InP Bipolar ICs: Scaling Roadmaps, Frequency Limits, Manufacturable Technologies. IEEE Proc 96(2), 271–286 (2008)Google Scholar
- 42.M. Urteaga, M. Seo, J. Hacker, Z. Griffith, A. Young, R. Pierson, P. Rowell, A. Skalare, V. Jain, E. Lobisser, M.J.W. Rodwell, InP HBTs for THz Frequency Integrated Circuits, presented at the 23rd International Conference on Indium Phosphide and Related Materials (2011)Google Scholar
- 43.M. Urteaga et al., A 130 nm InP HBT Integrated Circuit Technology for THz Electronics, 2016 IEEE International Electron Devices Meeting (IEDM) (2016), pp. 29.2.1–29.2.4Google Scholar