TCAD simulation of ion implantation test for controlling quality of GaAs substrates used for fabricating implanted devices

The quality of GaAs substrate material for manufacturing ion implanted devices is routinely determined by an ion implantation test. The test involves measuring an electrical quantity, such as sheet resistance, after implanting Si into the substrate. This work employs GaAs TCAD simulation to address the range of validity of the implantation test and the pitfalls associated with it. The results show that the electrical measurements are capable of discerning typical variation in the carbon concentration in the substrate. But, the surface or interface charge on GaAs, which may result from processing involved in wafer preparation, is also important. Therefore, while the implantation test in most cases is adequate to control the quality of the substrate, the test is susceptible to misinterpretation owing to the variations arising from the process involved in wafer preparation for the test.