| Multiple InP-channel high electron mobility transistors (HEMTs) with 1.0 {dollar}mu{dollar}m gatelengths and 5.0 {dollar}mu{dollar}m S/D spacings were designed, fabricated, and characterized for DC and RF operation at 300 an 80 K. The complex HEMT structures employing InP quantum well channels, ln{dollar}rmsb{lcub}0.52{rcub}Alsb{lcub}0.48{rcub}{dollar}As carrier donor and barrier layers, and {dollar}rm lnAs/lnsb{lcub}0.53{rcub}Gasb{lcub}0.47{rcub}{dollar}As ohmic cap layers were deposited by gas source molecular beam epitaxy (GS-MBE) using solid gallium, aluminum and indium sources and gaseous arsine and phosphine cracked at {dollar}900spcirc{dollar}C. S/D ohmic contacts were formed using a tunneling n{dollar}sp+{dollar}-lnAs/Ti/Au metallization scheme to yield specific contact resistances of 0.9-2.0{dollar}cdot{dollar}10{dollar}sp{lcub}-6{rcub} Omegacdot{dollar}cm{dollar}sp2.{dollar} Schottky gate diodes fabricated by surface state passivation of ln{dollar}rmsb{lcub}0.52{rcub}Alsb{lcub}0.48{rcub}As{dollar} in ((NH{dollar}sb4)sb2{dollar}S) solutions followed by Ti/Au metallization yielded improved barrier heights of 1.0-1.1 eV verses 0.40-0.55 eV for unpassivated gates.; The HEMTs were fabricated for enhancement (E-) and depletion (D-) mode operation. DC testing included analysis of Schottky current-voltage (IV) and common source transistor IV characteristics at 300 and 80 K. Improved gate properties, barrier heights and reverse bias current densities were observed with decreasing temperature. Cryogenic performance gains were also observed for HEMTs according to measurement of extrinsic transconductances, output conductances, knee voltages, saturation current densities, and source-drain (S/D) breakdown voltages.; InP-channel HEMT microwave characterization included 1-20 GHz frequency response measurements for E-HEMTs and D-HEMTs to 10 and 5V S/D bias, respectively. Microwave response measurements improved as the temperature decreased from 300 to 80 K. Analysis was based on calculations for short circuit current gain {dollar}(hsb{lcub}21{rcub}),{dollar} maximum unilateral transistor power gain {dollar}rm(Gsb{lcub}TU,max{rcub}),{dollar} maximum stable gain (MSG), unity current gain frequency (f{dollar}tau{dollar}), and maximum frequency of oscillation (f{dollar}rmsb{lcub}max{rcub}{dollar}). |
