Analysis of abrupt and linearly-graded HBTs with or without a setback layer

Analytical current equations for abrupt and linearly-graded heterojunctions with or without a setback layer have been derived. The equations are general and applicable to both abrupt and linearly-graded heterojunction bipolar transistors. Collector and base currents and small-signal parameters such as transconductance and cutoff frequency of the abrupt and linearly-graded heterojunction bipolar transistors with or without a setback layer are evaluated. Comparisons between the isothermal model, the numerical model, and the present model including self-heating effect are demonstrated.