A selective etching solution of GaAs over Al0.24Ga0.76As, composed of acid-buffer solution (citric acid monohydrate+potassium citrate) and H2O2, has been developed for GaAs/Al0.24Ga0.76As/In0.22Ga0.78As PHEMT applications. The best selectivity of 776 was achieved using the mixed solution (citric acid-buffer solution:H2O2 = 5:1). The etch rate of GaAs in the solution is as low as 46.6 angstroms/s. Both the low etch rate of GaAs and the high selectivity exhibit the standard deviation of pinch-off voltage of 1.0 μm-gate PHEMTs as low as ±0.029 V across a 3 in wafer. This demonstrates the applicability of this solution to the gate recess process.
All Science Journal Classification (ASJC) codes
- Electrical and Electronic Engineering