Gan/Algan Uv Photodiodes And Phototransistors

Using MOCVD grown GaN and AlGaN alloys and hetrostructures, we realized heterojunction UV photodiodes and phototransistors. We achieved photovoltaic internal quantum efficiency in excess of 90% and large UV-visible rejection ratio in the GaN/AlGaN PIN photodiodes. The results indicate high quality heterojunction interface and efficient carrier collection. We demonstrated an n-p-i-n GaN/AlGaN heterojunction bipolar phototransistor with gain in excess of 10(5), and 360 nm to 400 nm rejection ratio of 10(8). The phototransistor features a rapid electrical quenching of photoconductivity (PPC) therefore can be operated without DC drift, an option not available in unipolar photoconductors. The electrical bandwidth of the phototransistor can be changed to accommodate particular applications by simply adjusting the repetition rate of the quenching pulses. The operation and evaluation of the these devices are compared with alternative devices including SiC photodiode and GaN photoconductors.