National Institute of Advanced Industrial Science and Technology

Irspec Corporation

Katsuhiko Nishida

Mutsuo Ogura

SungWoo Choi

Nobuyuki Hayama

A hetero-junction bipolar phototransistor includes a photo-absorption layer formed of a first conductivity type semiconductor layer, and a collector operating as a barrier layer, a base layer, and an emitter layer, which are stacked in sequence on the photo-absorption layer. The photo-absorption layer, collector, base layer and emitter layer forms a first mesa structure, and an emitter contact layer forms a second mesa structure. The photo-absorption layer includes a semiconductor layer with a narrow gap corresponding to a light-sensing wavelength of the phototransistor. The collector includes a semiconductor layer with a wider gap than a gap of the photo-absorption layer. The base layer has an energy level equal to or higher than the energy level of the collector. The emitter layer has a wide gap as compared to the base layer, and an energy level in a valence band is lower than an energy level of the base layer.

Hetero-junction bipolar phototransistor with improved noise characteristic

An array structure solves issues that exist in conventional compound semiconductor photodiode arrays, such as large cross talk, large surface leaks, large stray capacitance, narrow detection wavelength bands, and bad manufacturing yield, simultaneously. A photodiode array has, laminated upon a semiconductor substrate, a buffer layer () with a broad forbidden band width, an I-type (low concentration photosensitive layer () with a narrow forbidden band width, and an n-type semiconductor window layer () with a broad forbidden band width, wherein photodiode elements are electrically separated from adjacent elements, by doping the periphery of the p-type impurity, and the detection wavelength band is expanded, by making the n-type window layer () on the photosensitive layer () a thinner layer with crystal growth.

Growing community of inventors

Tsukuba, Japan

Katsuhiko Nishida