Mixed P and N type conduction in RF sputtered Hg1-xCdXTe thin films

RF sputtered HgjCdTe thin films were deposited on <111> silicon substrates. Different values of negative bias were applied to the film during growth. X-ray diffraction was used to investigate the crystal structure of the films. Van Der Pauw and Hall measurements were used respectively to obtain resistivities and carrier concentrations of films at room temperature (3°K). Carrier concentration variation with temperature was also measured. A series of films were deposited with different substrate temperatures in order to investigate the effect on crystal structure and electrical properties. When substrate bias was increased, it was found that the film thickness decreased» the crystallographic order of the films became worse, and the room temperature resistivity increased. Measurement of carrier concentration versus temperature between 77°K and 3°K showed the films to be p type when the temperature was around 77°E and n type at high temperatures. It was also found that when the substrate temperature was increased during deposition, the crystal structure improved somewhat. Room temperature resistivity decreased, and the carrier type gradually changed from n type to p type as the deposition temperature was increased. A theoretical model using both a non-degenerate approximation as well as taking into account degenerate considerations was developed to compare with the experimental data