Characteristics of some experimental GaAs-Ge wide-gap emitter transistors fabricated by the epitaxial-diffusion process

Some theoretical aspects of the wide-gap emitter transistor will be reviewed and discussed briefly. A novel process which has been used to produce some experimental pnp wide-gap emitter transistors involving both the epitaxial and the diffusion processes will be described. The transistor uses the p-n GaAs-Ge heterojunction as the emitting junction and the n-p Ge homojunction as the collecting junction. Base width of the order of one micron or less can be obtained reproducibly. Experimental results of units made in the laboratory will be described with respect to the following: 1) Fabrication processes for making the experimental units. 2) The base width control. 3) The I-V and C-V characteristics of the emitter heterojunction and the collector homojunction. 4) The effect of crystal orientation on the geometry of the emitter heterojunction. 5) The current gain and the injection efficiency of the wide-gap emitter diffused-base transistor. The reproducibility of the transistor characteristics by the novel fabrication process has made possible the feasibility study and the evaluation of the wide-gap emitter transistor. Some aspects of the factors pertinent to the control of the fabrication process will also be discussed.