A GaAs/AlAs Wet Selective Etch Process for the Gate Recess of GaAs Power Metal-Semiconductor Field-Effect Transistors

Abstract

A highly selective wet chemical etch process for gate recess of the GaAs power metal-semiconductor field effect transistors (MESFETs) was developed. The power MESFETs used in this study were epitaxially grown devices with a 20 Å AlAs etch-stop layer for gate recess. The selective etch process using citric acid/potassium citrate/hydrogen peroxide solution was studied. A selectivity better than 3800:1 was achieved for GaAs/AlAs layers. This selective etch was applied both to high-power, high-voltage power MESFETs and low-voltage large-periphery power MESFETs. For high-power applications, the 14.7 mm device had a breakdown voltage of 22 V. When tested at 1.88 GHz with a drain bias of 10 V, it provided a maximum output power of 38.8 dBm and a maximum power-added efficiency of 52.5%. For low-voltage applications, the 19.8 mm device was tested under IS-95 code-division multiple access (CDMA) modulation at 1.88 GHz with a drain bias of 3.5 V. Under CDMA modulation, the device showed an output power of 28.03 dBm with an adjacent channel power rejection of −29.6 dBc at 1.25 MHz offset frequency. Both devices also showed excellent uniformity in pinch-off voltages. © 2000 The Electrochemical Society. All rights reserved.