Solar blind photodiode having an active region with a larger bandgap than one or both if its surrounding doped regions

Abstract

A solar blind p-i-n photodiode where the active i-region has a bandgap larger than the bandgap of one or both of the n-type and p-type regions. The preferred embodiment photodiode is GaN based and Al is added to the regions to obtain the desired bandgap profiles. Al is added to the i-region to obtain a bandgap large enough to be responsive to light in the solar blind spectrum. By having a smaller bandgap p-type and n-type region, the problems associated with growing highly doped AlGaN are avoided. In most embodiments the light incident on the photodiode illuminates the p-type region first. The p-type region is grown thin compared to conventional photodiodes which allows the majority of light incident to pass through the p-type region to the i-region. Light with sufficient energy will be detected in the i-region. The inventive photodiode can also be used in the fabrication of backside illuminated solar blind photodiodes that are useful for photodiode arrays. The inventive photodiode can also be used in avalanche mode by applying a large reverse bias across the p-type and n-type regions.