ALGAAS/GAAS HETEROSTRUCTURES FOR HEMT APPLICATIONS GROWN BY CHEMICAL BEAM EPITAXY

AlGaAs/GaAs heterostructures were grown by chemical beam epitaxy using triisobutylaluminium, triethylgallium and pure arsine. AlGaAs bulk layers of high optical quality and AlGaAs/GaAs heterostructures with abrupt and sharp interfaces were obtained. The mirrorlike surface morphology was excellent, with defect densities of around 100 cm-2 and total absence of oval defects. The n-doping was performed with elemental silicon from a conventional effusion cell. Two-dimensional electron gases with mobilities of 68000 cm2/V . s at 77 K in single heterostructures and maximal carrier densities of 2 X 10(12) cm-2 in quantum wells doped from both barriers were found. High electron mobility transistors (gate length: 0.2 mum) were fabricated from the latter, with extrinsic transconductance of 330 mS/mm and cut-off frequencies of 72 and 144 GHz for current and unilateral power gain, respectively.