Design of a InP/In1−xGaxAsyP1−y/In0.53Ga0.47As emitter-base junction in a Pnp heterojunction bipolar transistor for increased hole injection efficiency

Starting with Burt’s envelope function theory, we calculate the transmission coefficients of holes across an ${\mathrm{InP/In}}_{\text{1−x}}{\mathrm{Ga}}_x{\mathrm{As}}_y{\mathrm{P}}_{\text{1−y}}/{\mathrm{In}}_{\mathrm{0.53}}{\mathrm{Ga}}_{\mathrm{0.47}}\mathrm{As}$ heterointerface while varying the width and gallium and arsenic fractions of the InP lattice-matched quaternary compound $\text{(x=0.47y).}$ While comparing our results to the case of an abrupt ${\mathrm{InP/In}}_{\mathrm{0.53}}{\mathrm{Ga}}_{\mathrm{0.47}}\mathrm{As}$ interface, we find that the transmission coefficients of both heavy- and light-holes can be enhanced significantly for a 60-Å-wide quaternary layer with an arsenic fraction $\text{y=0.4}$ $\text{(x=0.188).}$ This should lead to an enhanced hole injection efficiency of Pnp heterojunction bipolar transistors using the heterointerface analyzed here as an improved design of the emitter-base junction.