Electronic properties of diamond for high-power device applications

The generation and transport of impact-ionized electrons in diamond are investigated using secondary electron emission spectroscopy. By studying secondary electron emission from diamond surfaces having a negative electron affinity (NEA), the total transmitted intensity and the full energy spectrum of the internal electrons are revealed in the measurements. Electron yield and energy distribution measurements from C(100) and CVD diamond samples are analyzed as a function of incident beam energy and information is obtained on both the internal gain and electron energy distribution following impact ionization as well as the effects of the transport process on the internal electron distribution. High internal gain and efficient electron transport are inferred from an analysis of the very high yields measured from both samples. In fact, by fitting calculated yield curves to the measured yield data, we deduce a lower limit on the electron escape depth of similar to 5 mu m and similar to 1.3 mu m in the C(100) and CVD diamond samples, respectively. Energy spectra measured from the diamond samples contain an intense, low-energy peak whose energy position and width are independent of incident beam energy. Based on an analysis of the energy distribution data, a model of the impact-ionization process in diamond is presented. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.