High electric-field amorphous silicon p-i-n diodes: Effect of the p-layer thickness

Abstract

We present amorphous silicon p-i-n diodes able to sustain a reverse bias corresponding to 106 V/cm with a reasonably low leakage current. The influence of the p-layer thickness on the reverse bias current and the breakdown voltage is investigated. The high-voltage reverse current at room temperature is attributed to two different mechanisms: field enhanced thermal generation in the p-i interface region and, at the highest bias, electron injection through the p layer. Variable range hopping is also contributing to the low-temperature reverse current. Charge collection measurements after pulsed photogeneration were also performed up to the maximum voltage. No evidence for signal amplification is found, which sets a lower limit of 106 V/cm for impact ionization and avalanche phenomena.

Hydrogenated Amorphous Silicon Sensor Deposited on Integrated Circuit for Radiation Detection

“…The high reverse voltages needed to deplete the "thick" sensors and the deposition on ASIC surface thus strongly increase the sensor's leakage current, enhancing mechanisms negligible in commercial a-Si:H devices. An electric field enhancement of thermal generation of charges in the a-Si:H sensor (Poole-Frenkel mechanisms [17]) can explain the bias voltage dependence of the leakage current measured on thick a-Si:H sensors. Moreover, some very high localized electric fields in a TFA detector pixel could explain the high currents measured in the TFA detectors.…”

“…7). A current induced by thermal generation enhanced by electric field through Poole-Frenkel mechanisms can be calculated as [17]: (1) (2) is the material bandgap, is the activation energy, i.e., the energy needed to activate ionisable defects, is the PooleFrenkel constant, the maximum current (for ), the temperature and the Boltzmann constant. Experimental data presented in Fig.…”

Hydrogenated Amorphous Silicon Deposited on the Asihtest Circuit for Radiation Detection

“…2. A current induced by thermal generation enhanced by electric field E through Poole-Frenkel mechanisms can be expressed as [7]:…”

Hydrogenated Amorphous Silicon Sensors Based on Thin Film on ASIC Technology

“…However, thicker layers are needed for particle detection. High reverse biases are required for full depletion of the sensor resulting in elevated electric field (> 10 4 V/cm) in the depleted region, and in increased leakage currents [13]. Results obtained on thick a-Si:H sensors (up to 32.6 µm) deposited on a glass substrate are presented in [2].…”

“…The thermal generation of charges is enhanced by the electric field by Poole-Frenkel mechanisms [13], so that local elevated fields in a pixel might create higher leakage currents. The pixel active area of a detector made of a 32.6 µm thick diode and of an AFP chip has been studied using a Scanning Electron Microscope (SEM).…”