Bulk and interfacial properties of the compositionally graded InxAl1−xAs (x≤0.52) quasi-insulator and its applications

Abstract

We have investigated the first in a series of compositionally graded quasi-insulator/semiconductor heterojunction (HJ) capacitors, intended to provide low interface state densities, low dc leakage currents, and high effective surface barriers. Molecular-beam epitaxy (MBE) was used to grow compositionally graded InxAl1−xAs quasi-insulators with x≤0.52 deposited on semiconducting In0.53Ga0.47As layers lattice matched to n+ -InP substrates. Interface states derived from electric field and temperature-dependent capacitance-voltage measurements have densities in the order of ≊1011/cm2 eV and have time constant distributions which are strongly dependent on compositional gradient. The surface barrier height also depends on the compositional gradient and the leakage current is decreased by three orders of magnitude from 10−6 to 10−9 A for a reverse bias of 1 V. Heterojunction insulated gate field-effect transistors (HIGFETs) with an intrinsic transconductance gm=125 mS/mm were obtained on a 5-μm-long gate structure.