Indium Doping of Hydrogenated Amorphous Silicon Film by Thermal Annealing

摘要

We report p-type doping of hydrogenated amorphous silicon (a-Si:H) films, by indium (In) deposition and thermal annealing. The annealing was carried out for two hours, at various annealing temperatures (T_a) in nitrogen gas (N_2) ambience. The dark conductivity (σ_d) and the activation energy (E_a) of the intrinsic a-Si:H film and the In deposited a-Si:H film were 4.7 × 10~(-11) S/cm, 1.7 × 10~(-10) S/cm and 0.79 eV, 0.63 eV respectively. The σ_d and E_a for the In deposited films, that were annealed at 200 ℃, 240 ℃ and 280 ℃ temperatures, were 3.8 × 10~(-8) S/cm, 5.8 × 10~(-8) S/cm, 7.8 × 10~(-9) S/cm and 0.47 eV, 0.49 eV, 0.57 eV respectively. Secondary ion mass spectroscopic (SIMS) depth profile shows that the indium diffusion length increases as the annealing temperatures increase (9.2 nm, 10.1 nm, 10.8 nm respectively). We have observed that the optical gap (E_g) of the films remain nearly unchanged at 1.92 eV for the annealed and un-annealed a-Si:H films that have In deposited, although Urbach energy (E_u) increased from 47 meV for In deposited a-Si:H film to 107 meV, 92 meV, 101 meV for the films annealed at 200 ℃, 240 ℃ and 280 ℃ temperatures respectively.