InGaP/InGaAs/GaAs pseudomorphic HEMT grown by solid source MBE

We report in here about the first pseudomorphic InGaP/InGaAs/GaAs HEMT demonstrator using an all solid source MBE technique. The quality of thick InGaP is found comparable to state of the art InGaP material grown by other methods. When inserted as part of a pHEMT structure, we found a very large etch selectivity of GaAs over InGaP using H₃PO₄:H₂O₂:H₂O solution. 100 μm wide device with a gate length of 5 μm have been fabricated using this selective wet etching technique. Au and AuGe/Au were used as Schottky gate and ohmic source-drain material, respectively, giving a Schottky barrier of 0.81±0.03 eV and lateral drain (or source) contact resistance of <0.1±0.01 Ω.mm. An extrinsic transconductance of 80.0±0.2 mS/mm was obtained. The large selectivity of GaAs over InGaP (approximately 100 times) leads to a simple, controllable and reproducible pHEMT process.