TRANSPORT-PROPERTIES OF N-CDS0.5SE0.5 P-INP HETEROJUNCTION CELLS/

Heterojunction cells of n-CdS0.5Se0.5/p-InP, fabricated by vacuum depo sition of CdS0.5Se0.5 thin films into InP single crystals, show a conv ersion efficiency as high as 5% and an open circuit voltage of 0.78 V under illumination by light with a power density of 50 mW m(-2). The C dS0.5Se0.5 films, nominally 400 nm thick, have resistivities of the or der of 10(-1) Omega cm, so that the film makes a good electrical conta ct between the junction and the front aluminium electrode. Measurement s of J- V and C- V characteristics also have been evaluated to identif y the mechanisms of barrier formation and current flow. At low voltage s, the current in the forward direction varies exponentially with the voltage. At higher voltages, two distinct regions of ohmic and space-c harge-limited conduction under forward bias are observed. The linearit y of the C-2- V dependence is associated with a homogenous distributio n of the impurities inside the space-charge region. Under a reverse bi as, the conduction process at low voltage is determined by Schottky em ission over a potential barrier of approximate height 0.88 eV and thic kness 98 nm. At higher voltage levels, the Poole-Frenkel effect is obs erved.