Ph.D Thesis

Ph.D StudentSheinman Benjamin
SubjectModeling and Performance of Ultrafast InP Based
Heterojunction Bipolar Transistors and Circuits
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROF. Dan Ritter


Indium phosphide based heterojunction bipolar transistors (HBTs) exhibiting record cutoff frequencies are a key building block of ultra fast circuits in optical communication systems and in other high frequency demanding applications.

In the first part of this study, a peeling algorithm for the direct extraction of the HBT equivalent circuit is given. A new scheme for the de-embedding of pad parasitics from the measured frequency response is given. The de-embedding is based upon measurement of the short and thru test fixtures instead of the traditionally used open and short test fixtures. A complete direct extraction algorithm following the de-embedding process is presented, to obtain transistor small signal model parameters.

The second part of the study explores charge dynamics in Np abrupt heterojunctions. It is shown that charge separation is prevented by the potential barrier at the base-emitter junction. As a consequence, no diffusion capacitance exists in these junctions. The lack of diffusion capacitance in an abrupt heterojunction is experimentally demonstrated.

In the third part of the study, the dynamics of base minority carriers in an abrupt heterojunction bipolar transistor are investigated. It is shown that only the collector current charges and discharges the minority carrier charge. In bipolar junction transistors (BJTs), for comparison, both emitter and collector currents charge and discharge minority carrier charge in the base. Small signal and large signal models of abrupt HBTs are presented and compared to BJT models.

In the last two sections of the study, a model for the influence of the vertical PIN photodiode spreading resistance on diode performance is given, and a low noise, low power, high gain monolithic transimpedance photo-receiver design, fabrication process and measurement is presented.