Fabrication and Characterization of Heterojunction Backward Diodes Based on the InAs/AlSb/GaSb Material System

Heterostructure backward diodes based on the InAs/AlSb/GaSb material system have been designed, fabricated and characterized. Fabrication processes have been developed based on conventional photolithography, wet chemical etching, planarization and passivation techniques. The performance of devices based on three different heterostructures is compared. Devices incorporating an Al0.1Ga0.9Sb anode instead of a GaSb anode show improved curvature coefficient. A junction capacitance of 15.5 fF/um^2 and a junction resistance of 2.5 kiloOhm*um^2 have been obtained on a structure with a p-GaSb anode. For a device with area of 7.6 um^2, a curvature coefficient of -20.9 V^(-1), a junction capacitance of 85.3 fF, and a junction resistance of 291.7 Ohm were obtained. Based on estimates of potential for contact resistance improvement and device scaling (down to 1 um^2), improvement of the intrinsic cut-off frequency to over 500 GHz appears possible for this structure. Johnson noise limited noise equivalent power (NEP) is estimated to be 1.05 pW/square root(Hz) for a conjugately-matched source. The detector's figures of merit can be further improved through additional optimization of the heterostructure and fabrication processes.