ELECTRICAL AND STRUCTURAL STUDY OF PARTIALLY RELAXED GA0.92IN0.08AS(P+)/GAAS(N) DIODES

The effects of in-plane lattice mismatch have been studied for Ga 0.92In0.08As(p+)/GaAs(n)/GaAs(n+) diodes. Different in-plane mismatch at the p-n junction was introduced by a variation of the GaInAs layer thickness (h=0.1, 0.25, 0.5, and 1 μm). Capacitance-voltage (C-V) measurements with different frequencies show a higher-frequency dispersion for a greater lattice-mismatched sample. From the frequency dependence of the C-V curve, single-level charged interface-state density (Ns) was estimated using the effective parallel capacitance and conductance components. The average charged interface density Nss was also estimated using Voltage-intercept (Vint) method. N ss shows a linear dependence on the in-plane mismatch. The charged interface state density is approximately 2.7 Δa∥/a 30 for partially lattice-relaxed heterojunctions. For the 1 μm sample, the forward I-V characteristic shows quasi-Fermi level pinning effect. Admittance spectroscopy measurement gives an equilibrium Fermi energy at about Ev+0.36 eV with hole capture cross section c p=2.7×10-15 cm2 for the 1 μm sample and at Ev+0.21 eV and cp=2.4×10-16 cm2 for the 0.5 μm sample.