Total Dark Current Research Articles

Excess low frequency noise/I-V studies in p-on-n MBE LWIR Hg1−xCdxTe detectors

Excess low frequency noise is investigated for the first time in infrared MBE grown LWIR Hg1−xCdxTe double layer planar heterostructure (DLPH) detectors grown on lattice matched substrates. LWIR detectors having R0Aopt values at 40K in the 101–107 Θ-cm2 range have been characterized as a function of temperature between 120 and 20K. Detectors with R0Aopt≥103Θ-cm2 at 40K have theoretical diffusion limited performance down to 78K and detectors with R0Aopt ≥105 Θ-cm2 at 40K are within a factor of two of theoretical diffusion limited performance for T>65K. Activation energies extracted from noise (Vd=−100 mV) and dark current (Vd=−100 mV) vs temperature measurements were detector dependent. The activation energy for detectors with R0Aopt≈106 Θ-cm2 at 40K is ∼0.90*Eg to 0.99*Eg. The noise measured between 78 and 105K in the intermediate performance (R0Aopt∼103–104 Θ-cm2 at 40K) detectors are higher than the noise measured in the higher performance (R0Aopt∼105–107 Θ-cm2) detectors. In addition, the excess low frequency noise and the dark current at −100 mV in the intermediate and poor (R0Aopt∼101 Θ-cm2) performance detectors are temperature independent. For each detector measured, the activation energy extracted from noise (Vd=−100 mV) vs temperature measurements is equal to the activation energy extracted from the total dark current (Vd=−100 mV) vs temperature measurements. For different dark current mechanisms, the excess low frequency noise varies with temperature and also with area within statistical accuracy in the same manner as the total dark current through the detector. At 78K, the Tobin14 expression holds in the general sense for equal area detectors dominated by different current mechanisms and also for detectors with a wide range of implant dimensions (Aimp=3.85×10−7 cm2 to Aimp=6.25×10−4 cm2). Following measurements, the detectors were stripped of the passivation and overlaying metal layers and dressed by a defect etch to reveal defects in each detector. A correlation among noise, leakage current and defect type has been determined for each detector.

A concept for a submillimeter-wave single-photon counter

We discuss the design for a submillimeter-wave photometer, using a combination of superconducting and single-electron devices, which would have high quantum efficiency, very low noise-equivalent powers, and eventually even submicrosecond timing resolution. The absorption of above-gap photons occurs in a small strip of superconducting Al, whose normal-state resistance can be matched efficiently to an antenna of a higher gap (Nb) superconductor. The quasiparticles produced by photon absorption are then confined via Andreev reflection, and forced to tunnel through a small SIS tunnel junction. The tunneling time is much shorter than the known (>10 /spl mu/s) quasiparticle recombination time, so collection efficiency will be high. The device sensitivity would be limited by the small subgap current in the high-quality Al/AlO/sub x//Al tunnel junction at temperatures (100 mK) well below T/sub c/. Scaling based on the larger junctions used in X-ray detector applications suggests that the total dark current can be <0.1 pA, or of order 10/sup 5/ electrons/second, corresponding to an NEP of less than 10/sup -19/ W//spl radic/Hz at 500 microns (600 GHz). The photocurrent will be measured using a fast single-electron transistor (RF-SET), which allows a shot-noise-limited performance even for the very small currents delivered from this low capacitance and high impedance SIS junction. Results of initial fabrication and dc characterization of an integrated photodetector are also given.

Formula omitted] noise and dark current components in HgCdTe MIS infrared detectors

1 f noise and dark current measurements on p-type Hg 0.71Cd 0.29Te Metal-Insulator-Semiconductor charge-integrating devices are presented. The contribution of different dark current components to total dark current and noise is analyzed. The unknown parameters are chosen as independent parameters within a reasonable range to fit to the experimental results. The dark current is calculated as a function of both temperature and device gate voltage. The results show that for the tested devices, the depletion dark current is dominant at the temperature range of 70–90 K, and the dark current caused by tunneling through Shockley-Read-Hall (SRH) centers is dominant at temperatures below 65 K. The discussion provides information in analyzing the origin of 1 f noise in Hg 0.71Cd 0.29Te MIS infrared detectors. This investigation is the first ever in-depth study of 1 f noise in HgCdTe MIS detectors as it relates to dark current components.

Construction and performance of diffused and ion-implanted silicon microstrip detectors

Two prototypes of silicon microstrip detectors, realized directly by our group either by ion implantation or by diffusion, are presented. The physical detector characteristics and their performances determined by exposing them to different radioactive sources are discussed, and a calculation of the different terms contributing to the total dark current is reported.

On refining gold and silver articles

The electrical performance of SiO2 passivated type-II superlattice double heterostructure photodiodes is demonstrated. Compared to unpassivated samples, a dark current of 4.009 × 10− 5 A/cm2 and the corresponding differential resistance-area of 165.82 Ω·cm2 at zero bias voltage are achieved at 77 K. The temperature-dependence and bias-dependence of the dark current are studied experimentally. According to fitting results, the existence of the SiO2 passivated layer alters the band bending at the interface, which influence the generation-recombination and trap-assisted tunneling current and then it is presented that the total dark current is reduced by introducing the SiO2 passivation technology. At 77 K, the corresponding spectral responsivity and detectivity of the samples are measured at a bias voltage of − 50 mV and the 100 % cutoff wavelength is determined to be 10.6 μm, which is fitted well with the simulation results of temperature dependence of experimental data.