Temperature Dependence of Minority Hole Mobility in n+-GaAs Measured with a New Variable Temperature Technique

The temperature-dependent mobility provides essential information for device design and serves as a sensitive probe of minority carrier scattering physics. As examples, dominant scattering mechanisms are identified by characteristic temperature dependencies of mobility and for low temperature bipolar device optimization, accurate minority carrier mobility data are required. We report the first temperature (T) dependent measurement of minority hole mobility in n⁺-GaAs. The minority carrier mobility (μ) was measured with the zero-field time-of-flight technique. In this technique, minority carrier diffusivity (D), where De = μkT, is determined from the transient response of a specially designed photodiode that is excited by a high-speed laser. We have extended the technique to permit continuously variable, T-dependent minority mobility measurements. The unique cryostat design, including device mounting, low-loss feedthroughs and temperature measurement scheme, is presented.