Background Limited Infrared Photodetector Research Articles

Study on the Theoretical Limitation of the Mid-Infrared PbSe N<sup>+</sup>-P Junction Detectors at High Operating Temperature

This paper provides a theoretical study and calculation of the specific detectivity-D* limit of photovoltaic (PV) mid-wave infrared (MWIR) PbSe n+-p junction detectors operating at both room temperature and TE-cooled temperature. For a typical PbSe p-type doping concentration of 2 × 1017 cm-3 and with high quantum efficiency, the D* limits of a photovoltaic PbSe n+-p junction detector are shown to be 2.8 × 1010 HZ1/2/W and 3.7 × 1010 HZ1/2/W at 300 K and 240 K, with cut-off wavelength of 4.5 μm and 5.0 μm, respectively. It is almost one magnitude higher than the current practical MWIR PV detector. Above 244 K, the detector is Johnson noise limited, and below 191 K the detector reaches background limited infrared photodetector (BLIP) D*. With optimization of carrier concentration, D* and BLIP temperature could be further increased.

P-InAsSbP/n-InAs single heterostructure back-side illuminated 8 × 8 photodiode array

P-InAsSbP/n-InAs/n+-InAs single heterostructure photodiode monolithic array with linear impurity distribution in the space charge region and “bulk” n-InAs absorbing layer has been fabricated by the LPE method and studied for the first time. Unlike all known InAsSbP/InAs PDs with an abrupt p-n junction the linear impurity distribution PDs potentially suggest lower compared with analogs capacitance and tunneling current. Indeed the developed photodiodes showed good perspectives for use in low temperature pyrometry as low dark current (8×10−6A/cm2, Ubias=−0.5V, 164K) and background limited infrared photodetector (BLIP) regime starting from 190K (2π field of view, D3.1μm∗=1.1×1012cmHz1/2/W) have been demonstrated. High photodiode performance is thought to be due to above peculiarities of the impurity distribution as well as low defect density in P-InAsSbP/n-InAs/n+-InAs single heterostructure.

Low dark current P-InAsSbP/n-InAs/N-InAsSbP/n+-InAs double heterostructure back-side illuminated photodiodes

P-InAsSbP/n-InAs/N-InAsSbP/n+-InAs double heterostructure photodiodes with linear impurity distribution in the space charge region have been fabricated and studied. The photodiodes showed good perspectives for use in low temperature pyrometry as low dark current (8·10−6A/cm2, Vbias=−0.5V, 164K) and background limited infrared photodetector (BLIP) regime starting from 150K (2π field of view, D3.1μm∗=1.4·1012cmHz1/2/W) have been demonstrated.

High quality mid-wavelength infrared InAs/GaSb superlattices by exploring the optimum molecular beam epitaxy growth process

In this paper we report on the growth of mid-wavelength infrared superlattice materials by molecular beam epitaxy. We focused on the effects of process parameters, such as arsenic beam equivalent pressure and shutter sequences, on the key material properties, such as the lattice mismatch and the surface morphology. Though a smaller As beam equivalent pressure helps to reduce the lattice mismatch between the superlattice and the GaSb substrate, the As beam equivalent pressure itself has a lower limit below which the material’s surface morphology will degrade. To achieve fully lattice-matched superlattice materials, a novel shutter sequence in the growth process was designed. With well-designed interface structures, a high quality P-I-N superlattice mid-infrared detector structure was realized. At 77K the dark current density at −50mV bias was 2.4×10−8A/cm2 and the resistance-area product (RA) at maximum (−50mV bias) was 2.4×106Ωcm2, and the peak detectivity was then calculated to be 9.0×1012cmHz1/2/W. The background limited infrared photodetector (BLIP) level can be achieved at a temperature of 113K.

Influence of Si doping on the performance of quantum dots-in-well photodetectors

The effects of doping on InAs∕In0.15Ga0.85As quantum dots-in-well infrared photodetectors have been investigated by measuring the dark current, photocurrent, spectral response, responsivity, and detectivity. The dark current increased monotonically as a function of the doping level in the dots. The photocurrent too increased with the increase in the doping level. By measuring the background limited infrared photodetector temperature, we find that the optimum sheet doping concentration in these detectors is n=3×1010cm−2 (corresponding to about 1e∕dot). These results were corroborated by measurement of responsivity and generation-recombination noise limited detectivity of these detectors.

Effects of Si doping on normal incidence InAs∕In0.15Ga0.85As dots-in-well quantum dot infrared photodetectors

The effects of doping on InAs∕In0.15Ga0.85As quantum dots-in-well infrared photodetectors have been studied by measuring the dark current, photocurrent, and spectral response. A significant reduction of dark current with decrease in doping concentration in the quantum dots has been observed. However, the photocurrent of the detectors increases with the doping. By measuring the background limited infrared photodetector temperature, we find that the optimum sheet doping concentration in these detectors is n=3×1010cm−2 (corresponding to about one electron per dot).

Two-dimensional infrared focal plane arrays based on HgCdTe photoconductive detectors

A novel photoconductive device structure is proposed and demonstrated that is suitable for use in two-dimensional infrared focal plane arrays (IRFPAs). The proposed device technology is based on the fabrication of high-performance long-wavelength infrared (LWIR) or mid-wavelength infrared (MWIR) photoconductors using epitaxially grown HgCdTe. Although the design concept can be applied to a variety of epitaxially grown HgCdTe materials, optimum performance is achieved using n-type HgCdTe semiconducting material consisting of epitaxially grown heterostructure layers in which a two-dimensional mosaic of photoconductors is fabricated. The heterostructure layers provide high-performance devices at greatly reduced power dissipation levels, while the unique contact design allows for the high-density integration of detectors in a two-dimensional array geometry with high fill-factor. The proposed photoconductor array with blocking contacts has been experimentally verified in a array format with all elements in the array exhibiting background limited infrared photodetector (BLIP) performance at 80 K.