AN ALGAAS/INXGA1-XAS/ALGAAS (0-LESS-THAN-OR-EQUAL-TO-X-LESS-THAN-OR-EQUAL-TO-0.5) PSEUDOMORPHIC HEMT ON GAAS SUBSTRATE USING AN INX/2GA1-X/2AS BUFFER LAYER

A new pseudomorphic HEMT employing a thick Inx/2Ga1-x/2As buffer layer on a GaAs substrate is proposed in order to use an InxGa1-xAs channel with a large InAs mole fraction. This buffer layer acts as a substrate with intermediate lattice constant. Transmission electron microscopy observations revealed that good-quality crystal can be obtained using this buffer layer. An extremely large 2DEG density of 4.6 × 1012 cm-2 was obtained at x = 0.4 with a high electron mobility of 15 500 cm2/V · s at 77 K. HEMT’s were fabricated on these wafers. The transconductance increases with increasing InAs mole fraction, and shows a peak at x = 0.4. The transconductance for 1.7-µm gate length was 500 mS/mm at room temperature, which was about 2.5 times larger than that of x = 0. © 1990 IEEE