Spectral response and field enhanced reverse current in a-Ge:H nip photodiodes

We demonstrate the effectiveness of using a high Ar+H₂ dilution of GeH₄, high pressure, and low substrate temperatures in producing device-grade a-Ge:H through standard radio-frequency glow discharge deposition. The enhanced plasma chemistry encourages the production, heating, and incorporation of nanoparticles to increase order, while the low substrate temperature encourages hydrogen incorporation to saturate dangling bonds. We utilize the material in nip photodiodes illuminated through the n-side, and demonstrate a device with an i-layer thickness of only 60 nm showing J_SC=20.6 mA/cm² (AM1.5 Efficiency=2.1%). Temperature-dependent conductivity and bias-dependent spectral response measurements suggest that a non-uniform field distribution and a defect-rich region near the i-p interface are currently the limiting factors for the device performance.