A novel Si-based LWIR detector: the SiGe/Si heterojunction internal photoemission detector

Long-wavelength Ge/sub x/Si/sub 1-x//Si heterojunction infrared detectors and 400*400-element imager arrays

“…As the wavelength increases above 1 pm, the quantum efficiency of the IrSi detector decreases monotonically, but the efficiency of the GeSi detectors initially increases, reaches a maximum of 0.6% to 1.0% at -3 pm, and then decreases. The initial increase in efficiency results from an increase in infrared absorption with increasing wavelength by the GeSi layer due to free-carrier absorption [ll] and interband transition [6]. Beyond the maximum, the efficiency decreases because the continuing increase in absorption is outweighed by the decrease in the probability of photoemission over the GeSi/Si heterojunction barrier as the photon energy and therefore the energy of the photoexcited carriers decreases.…”

“…The concept of utilizing internal photoemission over a heterojunction barrier for IR detection was first proposed [4] by Shepherd et al in 1971. Recently such a detector consisting of a heavily doped p+-Ge,Si, -, epitaxial layer and a p-Si substrate has been demonstrated [5], [6] to exhibit LWIR detection capability. The barrier height (which is determined by the valence-band offset), and therefore the detector cutoff wavelength, can be tailored by varying the composition of the Ge,Si,-, layer.…”

Long-wavelength stacked SiGe/Si heterojunction internal photoemission infrared detectors using multiple SiGe/Si layers

“…Especially, very long wavelength (13-17 pm) imaging is needed for the current NASA's Earth Observing System (EOS). Recently, with the advent of the silicon molecular beam epitaxy (Si-MBE) growth technique, novel SiGe/Si heterojunction internal photoemission (HIP) IR detectors have been fabricated and demonstrated to exhibit tailorable detector response in the long-wavelength infrared regime [1][2][3][4][5]. Furthermore, using SiGe/Si HIP detector elements and monolithic CCD readout circuitry, 400 x 400 and 320 x 244 focal plane arrays with 10 ~m cut-off wavelength were fabricated by Tsaur et.…”