Ey. Chang et al., A GaAs/AlAs wet selective etch process for the gate recess of GaAs power metal-semiconductor field-effect transistors, J ELCHEM SO, 148(1), 2001, pp. G4-G9
A highly selective wet chemical etch process for gate recess of the GaAs po
wer metal-semiconductor field effect transistors (MES FETs) was developed.
The power MESFETs used in this study were epitaxially grown devices with a
20 Angstrom A1As etch-stop layer for gate recess. The selective etch proces
s using citric acid/potassium citrate/hydrogen peroxide solution was studie
d. A selectivity better than 3800:1 was achieved for GaAs/A1As 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 GH
z 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 application
s, 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 modula
tion, the device showed an output power of 28.03 dBm with an adjacent chann
el power rejection of -29.6 dBc at 1.25 MHz offset frequency. Both devices
also showed excellent uniformity in pinch-off voltages. (C) 2000 The Electr
ochemical Society. S0013-4651 (00)03-053-6. All rights reserved.