Supported by Delco Electronics


The purpose of this report is to summarize the progress to date on the development of a 2D computer model for bipolar junction transistors. The goals of this project, which ends December 31, 1988, can be broken into two main categories and are listed below: Code Modifications 1. Modify existing 2D solar cell simulation code to handle bipolar junction transistors. 2. Incorporate energy balance equations into the computer model. 3. Incorporate transient and small signal ac analyses. Code Applications 1. Assess performance differences between Delco small and large thin epi devices. 2. Evaluate a polysilicon modification of the thin epi process. 3. Provide general analytic support. 4. Investigate extraction of SPICE parameters from simulation results. 5. Provide version of the code to Delco Electronics. The solar cell code, SCAP2D (Solar Cell Analysis Program in 2 Dimensions), has been successfully modified to handle bipolar junction transistors. This code has been named DAP2D (Device Analysis Program in 2 Dimensions). The major weakness of the code at the present time is its inability to model the Delco thin epi device adequately. The structure of this device is sufficiently complicated that computational restrictions in the present version of DAP2D require that simplifying assumptions be made when modeling this device. This problem is being addressed by the installation of a software package which will reduce the restrictions on device structure complexity (Chapter 3). Some simulation results are presented in Chapter 2. The most significant modeling result to date is the prediction that a factor of about 3 improvement in β can be expected with the addition of a polysilicon emitter contact. This result was obtained by assuming that the polysilicon contact can be modeled by an effective contact recombination velocity. Several appendices are also included in this report. Appendix A contains an overview of the numerical methods used to solve the semiconductor equations which are used to model device behavior. A user’s manual for DAP2D is presented in Appendix B. An example simulation is presented in Appendices C and D.

Date of this Version