Key Laboratory of Radiation Detection Materials and Devices, Ministry of Industry and Information Technology, School of Materials Science and Engineering, Northwestern Polytechnical University
The relaxation semiconductor is a material whose dielectric relaxation time is larger than its carrier lifetime, which is contrary to the lifetime semiconductor. The dielectric relaxation time is proportional to the resistivity, therefore relaxation semiconductors are typically highresistivity materials such as compensated semiconductors, amorphous semiconductors and semiconductors at low temperatures. In the relaxation semiconductor, due to the process to recover charge neutrality is slower than the recovery of the mass action law, space charges including free and trapped ones determine carrier transport behaviors. In the relaxation semiconductor, minority carrier injection leads to majority carrier depletion and neutral injection leads to separation of injected electrons and holes, while in the lifetime semiconductor lead to majority carrier accumulation and ambipolar transport, respectively. The majority carrier depletion can be characterized by the currentvoltage test and the frequency response test. The currentvoltage curve of the relaxation semiconductor contains an extended linear regime at low voltages and a superlinear regime at higher voltages. In addition, the curve is affected by trap concentration. The separation of photocarriers can be directly observed by carrier dynamics tests. Unique properties of the relaxation semiconductor have great application prospects in radiation detectors, radiationhardness devices, photoconductive switches, thermal sensors, etc.