High-resistivity GaN buffer templates and their optimization for GaN-based HFETs

High-resistance (HR) GaN templates for AlGaN/GaN heterojunction field effect transistor (HFET) applications were grown using organometallic vapor phase epitaxy. The GaN sheet resistance was tuned using final nucleation layer (NL) annealing temperature and NL thickness. Using an annealing temperature of 1033 degrees C and NL thickness of 26nm, GaN with sheet resistance of 10(10)Omega/sq was achieved, comparable to that of Fe-cloped GaN. Material characterization results show that the high-resistance GaN is achieved due to compensating acceptor levels that may be introduced through edge-type threading dislocations. Optimization of annealing temperature and NIL thickness provided a means to maximize GaN sheet resistance without significantly degrading material quality. In situ laser reflectance was used to correlate the NL properties to sheet resistance and material quality, providing a figure of merit for expected sheet resistance. AlGaN/GaN HFET layers grown using FIR GaN templates with R-s of 10(10)Omega/sq gave surface and interface roughness of 14 and 7 (A) over circle, respectively. The 2DEG Hall mobility and sheet charge of HFETs grown using FIR GaN templates was comparable to similar layers grown using unintentionally doped (UTD) GaN templates. (c) 2005 Elsevier B.V. All rights reserved.