Advances in Photodiodes 428At the same time these PDs are characterized by rather low values of the differential resistance -area product R 0 A at room temperature. This seems to be the main reason that InAs infrared photodetectors operate in sub-BLIP regime (Rogalsky, 1995). Further improvement in their performance is possible with a decrease in dark current and supression of Auger recombination. Preparation of photodiodes and experimental techniquesHomojunction PDs were prepared by short-term (20-30 min) diffusion of Cd into n-InAs substrates at T=875 K. The substrates of n-type conductivity were cut from single-crystal ingots grown in joint-stock company "Pure metals plant" (Svetlovodsk, Ukraine). The damaged surface layers were removed by using dynamic chemical-mechanical polishing in 2% Br 2 -CH 3 OH solution. Their structural quality was controlled by X-ray diffraction method. In the chemically polished substrates the rocking curves half-width was 25-27 '' . Electrical parameters were controlled by van der Pauw technique at 295 K. The carrier concentration and mobility were found to be n=(2÷3)×10 16 cm -3 and µ n =(2÷2.5)×10 4 cm 2 /V×s, respectively. The density of dislocations was in the range (2÷4)×10 4 cm 2 . The substrates with the diffused p-type layer had mirror-like surfaces free of structural damages such as inclusions of impurity atoms. They were characterized by the rocking curve halfwidth of 32-35 '' . Typical profiles of Cd atoms in a substrate are shown in Fig.1. As seen, at low values of depth x they can be approximated by two exponential dependences (shown by solid lines in Fig. 1). Similar profiles of impurity atoms were previously observed in GaAs (Grigor'ev & Kudykina, 1997) and explained by generation of non-equilibrium vacancies at the substrate's surface. In such a case, an impyrity profile is determined by distribution of vacancies under the surface. The junction depth was determined from the probe thermo-emf measurements during careful chemical etching of diffused layers. Mesa structures were prepared on (111)A side of substrates by chemical etching in 2% Br 2 -HBr solution. In order to eleiminate the surface leakage current mesas were passivated by etching in HNO 3 -based solution followed by deposition of anode oxide doped with fluorine with thickness of 0.3 m. After passivation they were covered by thin layer of ZnTe thermally deposited in a vacuum chamber at temperature 150 o C. The heterojunction p + -InAsSbP/n-InAs PDs were prepared by LPE technique in IOFFE Physico-Technical Institute, St.-Petersbur Russia (Zotova, 1991;Matveev, 1997;Matveev, 2002). For this purpose, lattice matched InAsSbP epitaxial layers of approximately 3 μm thickness were grown on (111)B surfaces of InAs substrates. The quaternary InAsSbP compound had energy gap of 0.43 eV at T = 297 K. The epilayers were doped to about 10 18 cm -3 by addition of Zn to the melt. The substrates were n-type single crystals with electron concentration n=(2÷3)×10 16 cm -3 . In homojunction and heterojunction PDs mesa struc...

Native defects in HgCdTe, including dislocations and defect complexes, can act as Shockley-Read-Hall (SRH) centers due to their effect on the carrier lifetime. There is a large literature concerning the links of deep defects to the carrier lifetime in

Abstract. InSb p-n junctions were prepared by three diffusion methods, including isothermal, two-temperature and two-stage diffusion processes. The current-voltage characteristics were measured as a function of temperature and bias voltage. The highest values of the resistance-area product at zero bias have been obtained for the junctions prepared using the two-stage diffusion process.

Abstract. The linearly-graded p-n junctions were prepared by diffusion of cadmium into n-InSb(100) substrate with the electron concentration n  1.610 15 cm -3 at the temperature T = 77 K. Passivation and protection of mesa structures have been carried out using thin films of CdTe. Forward and reverse current-voltage characteristics were investigated within the temperature range 77…156 K. It has been found that the total dark current consists of generation-recombination and tunneling current components, which are dominant at high (T = 120…156 K) and low (T < 120 K) temperatures, respectively. Experimental results have been explained using the model of a nonhomogeneous p-n junction. It has been shown that in the linearly-graded p-n junction with the rather thick (~1 m) depletion region tunneling current flows through the states related to dislocations in the depletion region. The performed estimation of electrical parameters of diffusion InSb p-n junctions allows to predict behavior of InSb-based photodiodes at operation temperatures T > 77 K.

The performance of infrared InAs homojunction and heterojunction photodiodes (PD) and possibilities of its improvement are analyzed both theoretically and experimentally. The figures of merit such as the resistance-area product R 0 A, the carrier lifetime and the quantum efficiency are studied. The excess carrier lifetime in InAs are calculated for radiative and Auger recombination mechanisms using three-and four-band Kane model. Theoretical limit of threshold parameters in InAs-based photodiodes is calculated for intrinsic (radiative and Auger) recombination processes. The diffused PD were prepared by short-term cadmium diffusion into substrates with n-type conductivity. In the investigated PD the total dark current is determined by the diffusion carrier transport mechanism at room temperature. Experimentally proved that heterojunction PD p + -InAsSbP/n-InAs can be more effective as sensitive element in gas sensors operated at room temperature in comparison with commercially available PD.Their threshold parameters (current sensitivity and detectivity) have approximately the same values as in commercially available photodiodes, but they have higher values of the resistance-area product.