Diode Reverse Leakage Current Research Articles

Improved performance in vertical GaN Schottky diode assisted by AlGaN tunneling barrier

In a vertical GaN Schottky barrier diode, the free electron concentration n in the 6-μm-thick drift layer was found to greatly impact the diode reverse leakage current, which increased from 2.1 × 10−7 A to 3.9 × 10−4 A as n increased from 7.5 × 1014 cm−3 to 6.3 × 1015 cm−3 at a reverse bias of 100 V. By capping the drift layer with an ultrathin 5-nm graded AlGaN layer, reverse leakage was reduced by more than three orders of magnitude with the same n in the drift layer. We attribute this to the increased Schottky barrier height with the AlGaN at the surface. Meanwhile, the polarization field within the graded AlGaN effectively shortened the depletion depth, which led to the formation of tunneling current at a relatively small forward bias. The turn-on voltage in the vertical Schottky diodes was reduced from 0.77 V to 0.67 V—an advantage in reducing conduction loss in power switching applications.

Fabrication and characterization of InAlN/GaN-based double-channel high electron mobility transistors for electronic applications

In our previous work [J. S. Xue et al., Appl. Phys. Lett. 100, 013507 (2012)], superior electron-transport properties are obtained in InAlN/GaN/InAlN/GaN double-channel (DC) heterostructures grown by pulsed metal organic chemical vapor deposition (PMOCVD). In this paper, we present a detailed fabrication and systematic characterization of high electron mobility transistors (HEMTs) fabricated on these heterostructures. The device exhibits distinct DC behavior concerning with both static-output and small-signal performance, demonstrating an improved maximum drain current density of 1059 mA/mm and an enhanced transconductance of 223 mS/mm. Such enhancement of device performance is attributed to the achieved low Ohmic contact resistance as low as 0.33 ± 0.05 Ω·mm. Moreover, very low gate diode reverse leakage current is observed due to the high quality of InAlN barrier layer deposited by PMOCVD. A current gain frequency of 10 GHz and a maximum oscillation frequency 21 GHz are also observed, which are comparable to the state-of-the-art AlGaN/GaN-based DC HEMT found in the literature. The results demonstrate the great potential of PMOCVD for application in InAlN-related device’s epitaxy.

Effects of Pre-Process Temperature Stressing on AlGaN/GaN HEMT Structures

AbstractIn an effort to investigate the stability of the surface and hetero-interface of AlGaN/GaN HEMTs during high temperature device processing steps, AlGaN/GaN HEMT samples were subjected to temperatures from 650°C to 1150°C for a period of 30 seconds prior to processing. Hall and photoluminescence measurements were performed on samples before and after temperature stressing. The samples annealed at 700°C and 1150°C were then processed, and electrical parametric data were collected during and after processing. Large increases in HEMT Schottky gate diode reverse leakage current are observed at higher pre-process annealing temperatures, while the low-field mobility decreases.

Failure Modes and Mechanisms of DC-Aged GaN LEDs

This paper presents failure modes observed in long-term aging of high-brightness GaN/InGaN LEDs. The blue LEDs submitted to DC aging test present large decrease of emitted optical power and increase of diode reverse leakage current. Increase of parasitic series resistance, suggesting contact degradation, has also been found in stressed sample, together with apparent carrier density increases and reduction of the junction depletion width. Furthermore stressed LEDs present modification of a specific trap property: trap activation energy decreases from 340 meV in the virgin sample down to 75 meV in the stressed sample. Generation of non-radiative recombination centers seems to be one of the dominant failure mechanisms responsible for the observed electrical and optical LED degradations.

1.3 μm photoresponsivity in Si-based Ge1−xCx photodiodes

Ge 1−x C x /Si heterostructure photodiodes with nominal carbon percentages (0⩽x⩽0.02), which exceed the solubility limit, were grown by solid source molecular beam epitaxy on n-type (100) Si substrates. The p-Ge1−xCx/n-Si photodiodes were fabricated and tested. The p-Ge1−xCx/n-Si junction exhibits diode rectification with a reverse saturation current of about 10 pA/μm2 at −1 V and high reverse breakdown voltage, up to −80 V. A significant reduction in diode reverse leakage current was observed by adding C to Ge, but these effects saturated with more C. Photoresponsivity was observed from these Si-based p-Ge1−xCx/n-Si photodiodes at a wavelength of ⩾1.3 μm, compatible with fiber optic wavelengths. External quantum efficiency of these thin surface-normal photodetectors was measured up to 2.2%, which decreased as the carbon percentage was increased.

Material and electrical properties of ultra-shallow p/sup +/-n junctions formed by low-energy ion implantation and rapid thermal annealing

A study of low-energy ion implantation processes for the fabrication of ultrashallow p/sup +/-n junctions is presented. The resulting junctions are examined in terms of four key parameters: defect annihilation, junction depth, sheet resistance, and diode reverse leakage current. In the realm of very-low-energy ion implantation, Ge preamorphization is found to be largely ineffective at reducing junction depth, despite the fact that the as-implanted boron profiles are much shallower for preamorphized substrates than for crystalline substrates. Transmission electron microscopy (TEM) analysis of residual defects after rapid thermal annealing (RTA) reveals that the use of either a preamorphization implant or the implantation of BF/sub 2/ as a B source results in residual damage which requires higher RTA temperatures to be removed. A reasonable correlation is observed between residual defect density observed via TEM and junction leakage current. It is concluded that the key to an optimized low-energy implantation process for the formation of ultrashallow junctions appears to be the proper selection of preamorphization and annealing conditions relative to the dopant implant energy. >

Hydrogenation of GaAs on Si: Effects on diode reverse leakage current

Plasma hydrogenation for 3 h at 250 °C of GaAs layers grown directly on Si substrates by metalorganic chemical vapor deposition, followed by a 5-min, 400 °C anneal to restore the passivated shallow donor electrical activity, increases the reverse breakdown voltage of Schottky diode structures from 2.5 to 6.5 V. This improvement appears to be a result of the passivation by atomic hydrogen of defects such as threading dislocations caused by the large (4%) lattice mismatch between GaAs and Si. A reduced Schottky barrier height is exhibited by hydrogenated samples, consistent with As depletion of the surface occurring during the long duration plasma processing.

Lifetime effects in ion implanted silicon

Abstract The damage produced by energetic ions in the space charge region of diffused p+n junction diodes is studied. By measuring the diode reverse leakage current, Jr , as a function of the implant parameters (ion mass. energy, post-anneal temperature, etc.) the characteristics of recombination-generation centers introduced by the implant process can be probed. It is these states which strongly affect the operation of lifetime dependent devices. The results can be fit by a single level Shockley-Read-Hall model with the centers lying ∼ 1kT from the centre of the gap. They are seen to be closer to the surface than the L.S.S. range of the implanted carbon ions. Silicon implants have reverse leakage currents which are roughly linearly dependent on dose for low doses while carbon and helium implants have highly super linear dependencies indicating that defects created by separate lighter ions can interact at low doses. The pre-implant reverse leakage current of diodes implanted with 1015/cm2, 300 keV C+ can be substantially but not completely recovered after a 75°C anneal.

Problems concerning the spatial distribution of deep impurities in semiconductors

Variation in the spatial distribution of recombination centres within a semiconductor causes difficulties in the interpretation of lifetime measurements. These difficulties are assessed for three methods of lifetime assessment; photoconductive decay, charge storage and diode reverse leakage current. A quantitative comparison of these methods is made on the basis of the simple model of a semiconductor consisting of a matrix of low recombination centre concentration containing embedded volumes of a much higher concentration. Under these conditions it is shown that the diode reverse leakage current is the most meaningful method of estimating the average recombination centre concentration. The charge storage method is seriously affected by clustering of recombination centres and the analysis shows how this method can be used to estimate qualitatively that clustering is present.

The Effects of Short Duration Neutron Radiation on Semiconductor Devices

Transistors, semiconductor diodes, and solid-electrolyte batteries were exposed to short duration, high-intensity neutron radiation from a U-235 critical assembly which was primarily a neutron source. The effect on these components was ascertained by comparing their principal parameters before and after exposure, and in several cases units of operating equipment utilizing these components were monitored during irradiation. Of the transistor electrical parameters altered by irradiation, most significant were the decrease in common emitter forward current gain (Beta) and the increase in collector diode reverse leakage current (Ico). The higher frequency units were less affected by neutron fluxes than were the audio transistors. High-frequency surface barrier transistors remained virtually undamaged by irradiation up to 1013 total neutrons per square centimeter, an exposure which rendered the audio units nearly useless. Semiconductor diodes suffered an increase in forward resistance and a decrease in back resistance in reasonable accord with the degree of neutron irradiation, while the solid-electrolyte batteries were not permanently affected. The results obtained are in reasonable agreement with those obtained by others who used pile-type reactors with much longer exposure times, thus indicating that the integrated neutron dosage is of primary significance rather than the rate of exposure. The degradation of performance of the operating equipment during irradiation was almost entirely attributable to changes in the semiconductor devices utilized therein.