Improved device performance by migration-enhanced epitaxy

Abstract

Migration-enhanced epitaxy (MEE) has been employed successfully to grow high quality GaAs buffer and InGaAs channel layers at 300°C. Planar-doped GaAs MESFETs with a thin MEE GaAs buffer layer have been fabricated for comparison with devices using conventional MBE buffers. Our preliminary data indicate that the MEE buffer alternative offers reduced side-gating effect, lower output conductance, better pinchoff characteristics and higher channel current. RF measurements indicate an improvement in output power density, gain and efficiency for the MEE-buffered MESFETs. High electron mobility transistor (HEMT) devices fabricated on modulation-doped pseudomorphic AlGaAs/InGaAs/GaAs heterostructures with a thin MEE buffer layer yield higher transconductance ( g m), transistor gain, and unity current gain cutoff frequency (ƒ T) compared to the conventional MBE-buffered devices. Moreover, HEMT devices with an MEE InGaAs channel grown at 300°C achieve comparable g m and ƒ T to those with a conventional MBE channel grown at ∼500°C. Critical layer thickness of InGaAs on GaAs using the MEE method, under the growth conditions reported here, is found to exceed that of MBE.