Two-dimensional electron gases in strained quantum wells for AlN/GaN/AlN double heterostructure field-effect transistors on AlN
- Department of Electrical Engineering, University of Notre Dame, Indiana 46556 (United States)
Double heterostructures of strained GaN quantum wells (QWs) sandwiched between relaxed AlN layers provide a platform to investigate the quantum-confined electronic and optical properties of the wells. The growth of AlN/GaN/AlN heterostructures with varying GaN quantum well thicknesses on AlN by plasma molecular beam epitaxy (MBE) is reported. Photoluminescence spectra provide the optical signature of the thin GaN QWs. Reciprocal space mapping in X-ray diffraction shows that a GaN layer as thick as ∼28 nm is compressively strained to the AlN layer underneath. The density of the polarization-induced two-dimensional electron gas (2DEG) in the undoped heterostructures increases with the GaN QW thickness, reaching ∼2.5 × 10{sup 13}/cm{sup 2}. This provides a way to tune the 2DEG channel density without changing the thickness of the top barrier layer. Electron mobilities less than ∼400 cm{sup 2}/Vs are observed, leaving ample room for improvement. Nevertheless, owing to the high 2DEG density, strained GaN QW field-effect transistors with MBE regrown ohmic contacts exhibit an on-current density ∼1.4 A/mm, a transconductance ∼280 mS/mm, and a cut off frequency f{sub T}∼104 GHz for a 100-nm-gate-length device. These observations indicate high potential for high-speed radio frequency and high voltage applications that stand to benefit from the extreme-bandgap and high thermal conductivity of AlN.
- OSTI ID:
- 22273407
- Journal Information:
- Applied Physics Letters, Vol. 104, Issue 19; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0003-6951
- Country of Publication:
- United States
- Language:
- English
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