Structural and electrical properties of (100) <i>β</i>-(Sc<i>x</i>Ga1−<i>x</i>)2O3/Ga2O3 heterojunctions

Abstract

Continuous composition-spread and heavily Si-doped β-(ScxGa1−x)2O3 (0.04 ≤ x ≤ 0.20) films were epitaxially grown on (100) β-Ga2O3 substrates by pulsed-laser deposition. The x dependence of structural and electrical properties was examined at room temperature. Vertical Schottky barrier diodes (SBDs) of Pt/β-(ScxGa1−x)2O3 with x ≤ 0.10 showed ideality factors of 1.6–1.7 and series resistance less than 10 mΩ cm2. In addition, the effective Schottky barrier height increased by ∼0.2 eV with increasing x from 0 to 0.10. The parasitic series resistance in SBDs with x &amp;gt; 0.10 increased exponentially as x increased, which was attributed to carrier localization in β-(ScxGa1−x)2O3 epilayers. This behavior was correlated with a sharp increase in the density of incoherent twin boundaries inherent in (100)-oriented β-Ga2O3-based epilayers. Moreover, the β-(ScxGa1−x)2O3/Ga2O3 interface with 0.04 ≤ x ≤ 0.11 accommodated two-dimensional electrons with a sheet density of 5–6 × 1012 cm−2, which is comparable to that observed at the (010) β-(AlxGa1−x)2O3/Ga2O3 interface. Our study demonstrates extended material designs for realizing modulation doping in β-Ga2O3 and its application to heterojunction field-effect transistors.