PARTICLE-INDUCED AND PHOTOINDUCED CONDUCTIVITY IN TYPE-IIA DIAMONDS

Electrical characteristics associated with radiation detection were me asured on single-crystal natural type-IIa diamond using two techniques : charged particle-induced conductivity and time-resolved transient ph otoinduced conductivity. The two techniques complement each other: The charged particle-induced conductivity technique measures the product of the carrier mobility mu and lifetime tau throughout the bulk of the material while the transient photoconductivity technique measures the carrier mobility and lifetime independently at the first few micromet ers of the material surface. For each technique, the mutau product was determined by integration of the respective signals. The collection d istance that a free carrier drifts in an electric field was extracted by each technique. As a result, a direct comparison of bulk and surfac e electrical properties was performed. The data from these two techniq ues are in agreement, indicating no difference in the electrical prope rties between the bulk and the surface of the material. The collection distance continues to increase with field up to 25 kV/cm without satu ration. Using the transient photoconductivity technique the carrier mo bility was measured separately and compared with a simple electron-pho non scattering model. The general characteristics of carrier mobility, lifetime, and collection distance at low electric field appear to be adequately described by the model.