The effect of hydrogen on the electronic properties of CVD diamond films

Thin film diamond, grown by chemical vapour deposition, have been found to display p-type surface conductivity. No bulk impurity is added to the films ; the p-type characteristics of the undoped diamond are thought to be due t o a surface or near surface hydrogenated layer. Carrier concentrations with in the range 10(17)-10(19) cm(-3) have been measured; control over the carr ier concentration can be achieved by annealing the 'as-grown' films in air. For a given annealing temperature a stable carrier concentration arises. T he Hall carrier mobility has been measured and a value of >70 cm(2)/Vs has been found for a film with a carrier concentration of similar to 5 x 10(17) cm(-3), the highest reported for polycrystalline thin film diamond and equ ivalent to boron doped single crystal diamond. I-V characteristics for Al-b ased Schottky diodes are good (ideality factor 1.1) and show no breakdown a t reverse bias levels greater than 100 V, suggesting this form of diamond i s well suited to electronic applications. (C) 1999 Elsevier Science S.A. AU rights reserved.