Electrical properties of n-amorphous/p-crystalline silicon heterojunctions

We have measured C-V characteristics and temperature dependence of J-V characteristics of undoped hydrogenated amorphous silicon (a-Si:H) heterojunctions formed on p-type crystalline silicon ( p c-Si) substrates with different resistivities. It has been found that an abrupt heterojunction model is valid for a-Si:H/p c-Si heterojunctions, and the electron affinity of a-Si:H has been estimated as 3.93±0.07 eV from C-V characteristics. The forward current of all the junctions studied shows voltage and temperature dependence expressed as exp(−ΔEa f/kT) exp(AV), where ΔEa f and A are constants independent of voltage and temperature, being successfully explained by a multitunneling capture-emission model. The reverse current is proportional to exp(−ΔEar/kT)(VD−V)1/2, where VD is the diffusion voltage and ΔEar is a constant. This current is probably limited by generation-recombination process.