High mobility of two-dimensional electron gas in a thin-tensile-GaN buffer based AlGaN/GaN high electron mobility heterojunction

In this paper, we report the properties of thin-GaN buffer based AlGaN/GaN high electron mobility transistor (HEMT) structures having tensile or compressive GaN buffer vis-a-vis the conventional HEMT with thick compressive GaN buffer. The MOCVD grown structures on SiC with 2000 nm, 200 nm, 150 nm and 100 nm GaN buffer were characterized for structural, morphological, and transport properties using X-ray diffraction, atomic force microscope and Hall measurement respectively. The stress in samples with 150 nm and 100 nm thin-GaN buffer were found to be tensile, unlike the compressive GaN buffer in the other two samples. The sheet carrier density and mobility of two-dimensional electron gas (2DEG) in 150 nm thin-tensile-GaN buffer based HEMT was found to be ∼ 1.1 × 1013 cm−2 and ∼ 2062 cm2/V·s; which is comparable to the results of conventional AlGaN/GaN HEMT with 2000 nm thick GaN buffer. Our results show that ∼150 nm thin-tensile-GaN buffer is optimum, wherein benefits of the thin-GaN buffer get combined with the enhanced mobility owing to the tensile strain in GaN.