Sensitivity Improvement in GaAsSb-Based Heterojunction Backward Diodes by Optimized Doping Concentration

An impedance-matched voltage sensitivity (β_v,opt) of 20400 V/W at 94 GHz was achieved at zero bias and room temperature using heterojunction backward diodes that were based on a p+-GaAsSb/i-InAlAs/n-InGaAs that was lattice matched to an InP substrate. Doping concentrations in the diodes were adjusted to optimize the sensitivity and its nonlinear characteristic. The proper donor doping concentration in n-InGaAs to increase its sensitivity was determined to be 1 × 10¹⁸ cm^-3. Meanwhile, the proper acceptor doping concentration in a p-GaAsSb layer was 5 × 10¹⁸ cm^-3 to achieve a large nonlinearity as a curvature coefficient (γ) of -49.4 V^-1, which exceeded that of ideal Schottky diode. The dependence of doping concentration on noise performance was also considered. The lattice-matched GaAsSb-based backward diodes are applicable in millimeter wave detectors and mixers.