Large-area low-capacitance InP/InGaAs MSM photodetectors forhigh-speed operation under front and rear illumination

Large-area long-wavelength metal-semiconductor-metal (MSM) photodetectors fabricated on the Fe-doped InP/InGaAs material system have been characterised under front and rear illumination employing different thicknesses of the photoactive layer. With a 350 μm diameter detection area, theoretically limited capacitance values (0.75 pF) and very low depletion voltages (<1 V) were obtained. For an active layer thickness of 0.7 μm, the devices show an external quantum yield of up to 60% and a bandwidth of 0.95 GHz at 10 V bias     

Influence of space charges on the impulse response of InGaAsmetal-semiconductor-metal photodetectors

The impulse response of interdigitated metal-semiconductor-metal photodetectors fabricated on an Fe-doped InGaAs absorbing layer and an Fe-doped InP barrier enhancement layer is investigated. For ultra-short pulse excitation of 150 fs at λ=620 nm the photoresponse is found to be less than 13 ps FWHM for detectors with 1 μm finger spacing. Above a certain level of illumination, the peak amplitude increases sublinearly and the relative contribution of the tail to the detector response is appreciably enhanced. The screening of the electric field by photo-generated space charges is responsible for this nonlinearity. For detectors with 5 μm finger spacing illuminated with 1.3 μm light pulses (FWHM=33 ps), space charge perturbation of the impulse response manifests itself by a decrease of the FWHM and an increase of the fall time with increasing illumination level. The practical consequences for the performance of MSM detectors in various applications are discussed     

High-speed metal-semiconductor-metal photodetectors on InP:Fe

Metal-semiconductor-metal (MSM) photodetectors on semi-insulating InP:Fe with a lateral planar structure have been fabricated. Laterally structured photodiodes are formed with interdigitated contact fingers. The detectors exhibit low dark currents of about 10 nA, an impulse response of 26 ps FWHM (full-width of half-maximum), and an internal quantum efficiency of 80%, all at 10 V bias. An electrical cutoff frequency of 40 GHz for the packaged detectors is obtained from s -parameter measurements, demonstrating that the response time is not limited by the parasitic elements of the devices     

High-performance large-area InGaAs metal-semiconductor-metalphotodetectors

The fabrication and characteristics of high-performance large-area InP:Fe/InGaAs:Fe/InP:Fe metal-semiconductor-metal (MSM) photodetectors are reported. With a 350-μm×350-μm active area, the detectors offer 900-MHz electrical bandwidth and 1.7-pF capacitance at 10-V bias. The respective dark current density is 20 pA/μm², an the CW responsivity is 0.4 A/W at 1.3-μm wavelength. The detectors are therefore ideally suited for applications in the long-wavelength range that require a large detection area and, at the same time, a high bandwidth and low capacitance