$\hbox {In}_{0.46}\hbox {Ga}_{0.54}\hbox {P}_{0.98} \hbox {Sb}_{0.02}/\hbox {GaAs}$ : Its Band Offset and Application to Heterojunction Bipolar Transistor

We report on the band alignment of In_0.46Ga_0.54 P_0.98Sb_0.02/GaAs and the dc characteristics of In_0.46Ga_0.54P_0.98Sb_0.02/GaAs heterojunction bipolar transistors (HBTs). By comparing the forward and reverse Gummel plot, we found a potential spike existing at the InGaPSb/GaAs interface. Through a flatband extrapolation from the currents of the forward and reverse Gummel plot and the energy gap determined from photoluminescence, we concluded that In_0.46Ga_0.54P_0.98Sb_0.02/GaAs is in a type-I band alignment. The conduction-band offset and valence-band offset are 0.12 and 0.35 eV, respectively. As a result of the type-I band alignment, the InGaPSb/GaAs HBTs showed a more significant thermal degradation of the current gain than the control InGaP/GaAs HBT. The thermal behavior is beneficial to ruggedness.