POLYCRYSTALLINE CVD DIAMOND FILMS WITH HIGH ELECTRICAL MOBILITY

Advances in the deposition process have led to dramatic improvements i n the electronic properties of polycrystalline diamond films produced by chemical vapor deposition (CVD). It is now possible to produce CVD diamond with properties approaching those of IIa natural diamonds. The combined electron-hole mobility, as measured by transient photoconduc tivity at low carrier density, is 4000 square centimeters per volt per second at an electric field of 200 volts per centimeter and is compar able to that of the best single-crystal IIa natural diamonds. Carrier lifetimes measured under the same conditions are 150 picoseconds for t he CVD diamond and 300 picoseconds for single-crystal diamond. The col lection distance at a field of 10 kilovolts per centimeter is 15 micro meters for the CVD diamond as compared to 30 micrometers for natural d iamonds. The electrical qualities appear to correlate with the width o f the diamond Raman peak. Also, although the collection distance at th e highest fields in the films nearly equals the average grain size, th ere is no evidence of deleterious grain boundary effects.