Thick (∼ 50 μm) amorphous silicon p-i-n diodes for direct detection of minimum ionizing particles

Thick (∼ 50 μm) amorphous silicon (a-Si:H) p-i-n diodes of device quality are made by helium dilution of the process gas and heat treatment for application to minimum ionizing particle detection. Dilution of SiH₄ with He decreased the dangling bond density and increased the deposition rate. The internal stress, which causes substrate bending and delamination, was reduced by a factor of 4 to ∼ 90 MPa when deposited at low (150°C) temperature. The electronic quality of the a-Si:H film was somewhat degraded when grown at a low temperature, but could be mostly recovered by subsequent annealing at 160°C. By this technique 50 μm thick n-i-p diodes were made without significant substrate bending, and the electronic properties, such as electron mobility and ionized dangling bond density, were suitable for detecting minimum ionizing particles. Diode readouts and integrated amplifiers for pixel arrays are also described.