Effect of two step GaN buffer on the structural and electrical characteristics in AlGaN/GaN heterostructure

Abstract

AlGaN/GaN hetero-structure based High electron mobility transistor (HEMT) is one of the emerged electronic devices for high power and high frequency applications. In this report, MOCVD grown AlGaN/GaN heterostructure on silicon carbide (SiC) substrate's structural, morphological and electrical characteristics have been studied and reported. In the article, the growth and characterization of a single-step and two-step GaN buffered AlGaN/GaN multilayer samples are presented. The study demonstrates the reduction in the threading dislocation density (TDDs), surface/interface roughness and enhancement in electron mobility in two-step GaN buffered sample as compared to single-step grown GaN buffered AlGaN/GaN structures. Two-step grown GaN buffer used AlGaN/GaN HEMT structure shows high crystalline quality, low Threading dislocation density (TDDs) ~1.2 × 109/cm2, smooth step flow surface morphology (surface roughness ~0.28 nm, interface roughness ~ 0.5 nm) and better 2DEG (two-dimensional electron gas) electron mobility~1913 cm2/V-sec at room temperature. The obtained results are an important step in the optimization of improved device quality of AlGaN/GaN HEMT structure on the silicon carbide substrate.