Intra-valance transitions for uncooled short wave infrared detection

An infrared detector based on p-GaAs/AlGaAs heterojunction exhibiting response in the 2-5 $\mu $m range at room temperature is demonstrated. The basic principle of the detector utilizes inter-valance (heavy hole, light hole, and split-off hole) absorption of a highly p-doped GaAs layer (emitter). The dark current is limited by the work function at the interface between the highly doped emitter and the undoped Al$_{x}$Ga$_{1-x}$As barrier. The barrier height can be tailored by varying the Al fraction to obtained the desired operating temperature. The split-off energy of the material determines the split-off threshold and the band offset determines the free carrier threshold for the photo excited carriers. Detector performance can be controlled by varying these two thresholds. A device consisting of 30 periods of 3$\times $10$^{18}$ cm$^{-3}$ p-doped GaAs emitter and Al$_{0.57}$Ga$_{0.43}$As barrier regions between two contact layers shows infrared detection up to 330 K with a peak responsivity of 1.4 A/W and D* of 2.6$\times $10$^{9}$ Jones at 2.5 $\mu $m . Different materials should give rise to different wavelength threshold infrared detectors operating at high temperatures.