Pecvd Grown p-i-n Si and Si,Ge Thin Film Photodetectors For Integrated Oxygen Sensors

Recent efforts to advance photoluminescence (PL)-based oxygen sensors have focused on developing compact, field-deployable devices. This has led to organic light emitting device (OLED)-based sensors with a structurally integrated [OLED excitation source]/[sensing film] module. To additionally integrate a photodetector (PD), PECVD for fabrication of thin-film p-i-n and n-i-p Si- and Si,Ge-based PDs was employed. O2 concentrations are advantageously determined by monitoring the effect of O2 on shortening the PL decay time  of an oxygen-sensitive dye, rather than on quenching its PL intensity. This approach, which employs pulsed OLEDs, eliminates the need for frequent sensor calibration, minimizes issues associated with background light, and eliminates the need for optical filters, which lead to bulkier sensors. However, it requires PDs with response times significantly shorter than . Therefore, the development of thin-film PDs focused on decreasing their response time, and understanding the factors affecting it. In this paper we show that boron diffusion during growth from the p+ to the i layer increases the response time of PECVD grown p-i-n PDs. Incorporating a SiC buffer layer and fabricating superstrate structures, where the p+ layer is grown last, decrease it. Additionally, ECR fabricated PDs show a slower response in comparison to VHF PECVD-grown PDs.