Molecular beam epitaxial growth and device performance of metamorphic highelectron mobility transistor structures fabricated on GaAs substrates

Single and double pulse doped metamorphic high electron mobility transistor (MHEMT) structures have been grown on GaAs substrates by molecular beam ep itaxy. A linear indium graded buffer layer was used to expand the lattice c onstant. Transmission electron microscopy cross sections showed planar inte rfaces. Threading dislocations were not observed along both cleavage direct ions. For a single pulse doped MHEMT structure with an In0.56Ga0.44As chann el layer, the mobilities (10030 cm(2)/V s at 292 K; 32 560 cm(2)/V s at 77 K) and sheet density (3.2 x 10(12) cm(-2)) were nearly equivalent to values obtained for the same structure grown on an InP substrate. Secondary ion m ass spectroscopy measurements of a double pulse doped structure indicated n o measurable migration of the silicon doping pulses. MHEMT devices with 0.1 5 mu m gales were fabricated, tested, and compared to GaAs pseudomorphic HE MT devices of the same geometries. Above 9 GHz, the MHEMT devices exhibited lower noise figure. From 3 to 26 GHz, the associated gain was 3 dB higher with the MHEMT devices. Also higher linearity performance was obtained with the MHEMT devices. At 4 GHz MHEMT linearity measurements yielded third ord er intermodulation distortion intercepts, IP3, of 36-39 dBm with linearity figure of merits of 60-90. Due to the significantly lower cost and more rob ustness of GaAs substrates compared to InP substrates, MHEMT technology is very promising for low cost manufacturing of low noise amplifiers. (C) 1999 American Vacuum Society. [S0734-211X(99)01503-6].