Increase In Reverse Leakage Current Research Articles

Simulation study for anode engineering of AlGaN/GaN double-channel hybrid anode Schottky barrier diode

In this work, a new structure of double-channel hybrid anode Schottky barrier diode with dual anode metal (DCH-DM-HAD) was proposed, and the preliminary investigation of the device's electrical characteristic was conducted by using Silvaco TCAD tools. The double-channel hybrid anode diode (DCH-HAD) and single channel hybrid anode diode (SCH-HAD) were compared and it was found that the Ron at lower forward bias is twice as large as the higher bias, which is attributed to different Von of upper channel and lower channel. It can be avoided by setting different metal structures at anode. Besides, the Von decreases with increasing thickness of the barrier layer, but the reverse leakage current increases fast. Finally, the breakdown voltage of three different structures of hybrid anode diodes were compared, and it is found that replacing nickel with tungsten is harder to form uniform electric field due to difference of workfunction of tungsten and nickel. Nonetheless, these kinds of diodes own excellent electrical characteristics.

Strategically constructed AlGaN doping barriers for efficient deep ultraviolet light-emitting diodes.

Here, we propose a sandwich-like Si-doping scheme (undoped/Si-doped/undoped) in Al0.6Ga0.4N quantum barriers (QBs) to simultaneously promote the optoelectronic performances and reliability of deep ultraviolet light-emitting diodes (DUV-LEDs). Through experimental and numerical analyses, in the case of DUV-LEDs with conventional uniform Si-doping QB structure, severe operation-induced reliability degradation, including the increase of reverse leakage current (IR) and reduction of light output power (LOP), will offset the enhancement of optoelectronic performances as the Si-doping levels increase to an extent, which hinders further development of DUV-LEDs. According to a transmission electron microscope characterization and a numerical simulation, an improved interfacial quality in multiple quantum wells (MQWs) and more uniform carrier distribution within MQWs are demonstrated for our proposed Si-doping structure in comparison to the uniform Si-doping structure. Consequently, the proposed DUV-LED shows superior wall-plug efficiency (4%), IR at -6 V reduced by almost one order of magnitude, and slower LOP degradation after 168-h 100 mA-current-stress operation. This feasible doping scheme provides a promising strategy for the high-efficiency and cost-competitive DUV-LEDs.

Heavy Ion Induced Degradation Investigation on 4H-SiC JBS Diode with Different P+ Intervals

The heavy ion radiation response and degradation of SiC junction barrier Schottky (JBS) diodes with different P+ implantation intervals (S) are studied in detail. The experimental results show that the larger the S, the faster the reverse leakage current increases, and the more serious the degradation after the experiment. TCAD simulation shows that the electric field of sensitive points directly affects the degradation rate of devices with different structures. The large transient energy introduced by the heavy ion impact can induce a local temperature increase in the device resulting in lattice damage and the introduction of defects. The reverse leakage current of the degraded device is the same at low voltage as before the experiment, and is gradually dominated by space-charge-limited-conduction (SCLC) as the voltage rises, finally showing ballistic transport characteristics at high voltage.

Influence of heavy ion irradiation and high temperature on the performance of 4H–SiC Schottky barrier α particle detector

Traditional semiconductor detectors such as silicon and germanium are easily affected by ambient temperature and charge-particle ion's radiation. They can't work stably in harsh environments such as high temperature and strong radiation for a long time. In this paper, 4H-silicon carbide detectors based on a Schottky barrier diode (SBD) were fabricated and the combined influences of high temperatures and heavy ion irradiation on 4H–SiC detectors have been investigated. With no radiation, the 4H–SiC detectors have excellent I–V characteristics performance during a temperature range of 30–200 °C. Even at an ambient temperature of 200 °C, the leakage current of the 4H–SiC detector was only 107 nA at the full depletion voltage. Then 280 KeV C4+ heavy ions were used to irradiate the 4H-silicon carbide detectors, and the performances of the irradiated detectors were studied for different radiation doses from 1 × 1013 to 1 × 1016 ions/cm2 in a certain higher ambient temperature environment. For the fully depleted 4H-silicon carbide detectors in an ambient temperature of 140 °C, both the I–V characteristics and the energy resolution have shown a certain radiation damage at the radiation fluence of 1 × 1015 ions/cm2, while a significant deterioration was observed when the radiation fluence is up to 1 × 1016 ions/cm2. It means that the 4H–SiC detectors can withstand an irradiation dose of 1 × 1015 ions/cm2 at 140 °C. The time-dependent I–V curves were also investigated for the irradiated detectors for a standing time up to 192 h, and it's found that the irradiated detectors had minor changes in the leakage currents during a long time standing. A PN junction model with current and voltage equations was used to explain the phenomenon that the reverse leakage current increases with the increase of temperature. The surface recombination model was also used to explain the deterioration of I–V characteristics and energy resolution after irradiation.

Effect of Schottky annealing temperature on reverse leakage current of 6500 V 4H-SiC JBS diodes

Annealing treatment has an important effect on the electrical properties of Schottky diodes. In this paper, the effect of Schottky annealing temperature on reverse leakage current of 6500 V 4H-SiC JBS diodes was studied. The reverse leakage current of the diode annealed at 500 °C is higher than that of the diode annealed at 450 °C. This is because the Schottky barrier height of the diode annealed at 500 °C is decreased by 0.08 eV, which leads to a large reverse leakage current. Meanwhile, the Schottky barrier height of the diode annealed at 500 °C is decreased more significantly with the increase of measurement temperature, therefore the reverse leakage current increases significantly.

A SiC sidewall enhanced trench JBS diode with improved forward performance

A new high-performance sidewall enhanced trench junction barrier Schottky (SET-JBS) diode is proposed in this article. In the proposed SET-JBS diode, in addition to the Schottky contact on the top anode, the sidewall of the trenches also introduces Schottky contacts, which not only increases the Schottky contact area, but also weakens the junction field-effect transistor effect of the device, resulting in a high forward current density and a low specific on-resistance (R on,sp) with a small increase in reverse leakage current (J L). Simulation results show that the R on,sp of the proposed SET-JBS diode is reduced by 21.6%–46.7% with less than an order of magnitude increase in leakage current compared with that of the conventional trench JBS (T-JBS) diode when the trench distance is from 2.1 μm to 1.2 μm at the 2 μm trench depth. And the SET-JBS diode also performs better than the trench MOS barrier Schottky (TMBS) diode when comprehensively considered the R on,sp and J L. And the figure of merit and the trade-off relationship between the R on,sp and the breakdown voltage of the proposed SET-JBS both are better than those of the conventional T-JBS diode and TMBS diode. The forward I–V analytical model of the SET-JBS is also proposed, which is in good agreement with the simulation results. All the simulation results indicate that the proposed SET-JBS diode has promising potential in power electronics applications.

High-temperature (350 °C) oxidized iridium Schottky contacts on β -Ga2O3

Oxidized iridium (IrOx) Schottky contacts (SCs) with excellent high temperature stability were fabricated on 2¯01 β-Ga2O3 single crystal substrates. These IrOx:β-Ga2O3 SCs were operated at temperatures from 24 to 350 °C with only a very small increase in reverse leakage current, while maintaining extremely high rectification ratios (at ±3 V) of more than 10 orders of magnitude at all temperatures, including 350 °C. This remarkable high temperature performance was due to their very high and thermally stable rectifying barriers that, after an initial heat-related improvement, were characterized by zero-bias effective barrier heights of 2.05 ± 0.02 eV and ideality factors of 1.05–1.10, which were almost unchanged by further repeated operation at 350 °C. The reverse leakage current density at 350 °C was only ∼2.3 × 10−9 A cm−2 (∼3.0 pA) at −3 V and ∼7.5 × 10−8 A cm−2 (∼100 pA) at −100 V. These IrOx:β-Ga2O3 SCs represent a significant improvement in high-temperature β-Ga2O3 SC performance, with considerable potential for the fabrication of high temperature β-Ga2O3 rectifying diodes, deep UV photodetectors, and metal-semiconductor field effect transistors.

Effect of Gamma Irradiation on Electrical Properties of CdTe/CdS Solar Cells

The effect of Co-60 Gamma irradiation on electrical characteristics of CdTe/CdS solar cell has been analyzed using in-situ current-voltage characterization (I-V) in dark condition. The irradiation was done over a wide range of doses from 1kGy to 100 kGy. Electrical parameters such as ideality factor (n), series resistance (RS) and reverse bias leakage current (IR) for each dose have been calculated from the I-V characteristics. The ideality factor of the pristine solar cell is found to be 1.80 and it gradually increased up to 3.38 for the dose of 10 kGy, then it is around 3.38-3.61 for higher doses up to 100 kGy. The I-V characteristics showed significant increase in forward bias and drastic increase in reverse leakage current. The value of IR is 16.8 µA for pristine solar cell and it increases to 1.46 mA for 10 kGy. Further there is four times observable change in the value of IR. However the value of Rs is 0.80 ohm for pristine and continuously decreases to 0.34 ohm for 50 kGy dose. Further there is slight increase in the series resistance to 0.38 ohm for 100 kGy dose.

Effects of Gd2O3 Gate Dielectric on Proton-Irradiated AlGaN/GaN HEMTs

AlGaN/GaN high electron mobility transistors (HEMTs) and MOS-HEMTs using Gd2O3 as gate dielectric were irradiated with 2-MeV protons up to fluence of $1 \times 10^{15}$ cm−2. Results showed that proton irradiation causes a strong degradation in the Schottky gate devices, featured by more than three orders of magnitude increase in reverse leakage current, a 30% decrease in maximum drain current, and the same percentage of increase in ON-resistance, respectively. Scanning transmission electron microscopy showed that radiation induced a diffusion of Ni into Au in the gate and void formation, degrading the transistors’ characteristics. The Gd2O3 gate dielectric layer prevented this diffusion and void formation. MOS-HEMTs with Gd2O3 gate dielectric show 50% less decrease of performance under proton irradiation than Schottky gate HEMTs (conventional HEMTs). The trapping effects of Gd2O3 gate layer before and after irradiation are also discussed.

Recrystallization effects of swift heavy 209Bi ions irradiation on electrical degradation in 4H-SiC Schottky barrier diode

In this paper, the phenomenon that the recrystallization effects of swift heavy 209Bi ions irradiation can partially recovery damage with more than 1×1010ions/cm2 is investigated by the degradation of the electrical characteristics of 4H-SiC Schottky barrier diode (SBD) with swift heavy ion irradiation. Deep level transient spectroscopy (DLTS) and Current-Voltage (I-V) measurements clearly indicated that E0.62 defect induced by swift heavy ion irradiation, which was a recombination center, could result in the increase of reverse leakage current (IR) at fluence less than 1×109ions/cm2 and the recovery of IR at fluence more than 1×1010ions/cm2 in 4H-SiC SBD. The variation tendency of IR is consisted with the change of E0.62 defect. Furthermore, it is reasonable explanation that the damage or defect formed at low fluence in SiC may be recovered by further swift heavy ion irradiation with high fluence, which is due to the melting with the ion tracks of the amorphous zones through a thermal spike and subsequent epitaxial recrystallization initiated from the neighboring crystalline regions.

Effects of Annealing Pressure and Ambient on Thermally Robust RuOx Schottky Contacts on InAlN/AlN/GaN-on-Si(111) Heterostructure

We have shown that RuOx based Schottky contacts have good potential as the anode and gate electrode in III-nitrides high power diodes and high electron mobility transistors, respectively, owing to their low leakage current1. We have also found that the electrical characteristics of RuOx Schottky contacts depend on the annealing ambient and/or pressure, namely RuOx Schottky diodes annealed in N2 exhibit better thermal stability and lower leakage current compared to those annealed in vacuum. This is believed to be related to the oxidation of RuOx to RuO2 in N2 annealing and the reduction of RuOx to Ru in vacuum annealing. Between N2 and vacuum annealing, there are differences of pressure and ambient. Hence, it is not clear if the formation of RuO2 or the reduction to Ru from RuOx is related to the annealing pressure or ambient, or both. This motivates us to investigate the effects of annealing pressure and ambient on the electrical and material characteristics of RuOx Schottky diodes by conducting annealing in vacuum, N2 and Ar, with annealing in N2 and Ar performed at the same pressure. RuOx Schottky diodes fabrication process began with Ohmic contact patterning on InAlN/AlN/GaN-on-Si(111) substrates with a sheet resistance of 490Ω/□. The Ohmic contacts (Hf/Al/Ta) were then deposited and formed by the lift-off process, followed by annealing at 600oC in vacuum for 1 minute. After Schottky contact patterning (RuOx) was sputter-deposited in Ar and O2 plasma with 2:1 flow-rate ratio. During RuOx deposition, the substrates were not heated. The Schottky contacts were also formed by means of the lift-off process, and were annealed at 800oC under different pressures and ambients (in vacuum at a pressure of 6.67 × 10-3Pa, in N2 and Ar at the same pressure of 101.3kPa) for 1 minute to study their effects on the electrical and material characteristics of RuOx Schottky contacts. RuOx Schottky diodes without annealing have a reverse leakage current of ~18.0±2.1mAcm-2 at the bias voltage of -20V (see Figure 1(a)) and Schottky barrier height (SBH) of ~0.754±0.072eV. With vacuum annealing at the pressure of 6.67×10-3Pa, the reverse leakage current increases by one order of magnitude and SBH drops to 0.546±0.050eV. In contrast, the reverse leakage currents of both RuOx Schottky diodes annealed in N2 and Ar at the same pressure (~101.3kPa) decrease by 2 orders of magnitude and SBH increases by ~0.177eV compared to those of RuOx Schottky diodes without annealing. Since the electrical characteristics of RuOx Schottky diodes with either N2 or Ar annealing are similar, and different from those with vacuum annealing, it may be deduced that the annealing pressure, and not the ambient, is the reason for the differences observed. To substantiate this, we conduct X-ray Diffraction (XRD) characterisations of our samples, as shown in Figure 1(b), where RuOx Schottky contact without annealing is observed to be amorphous. With vacuum annealing at pressure of 6.67×10-3Pa and temperature of 800oC, only Ru phases are formed and no RuOx phase is observed, owing possibly to the dissociation of Ru and O bond in RuOx. This agrees well with the relationship between the dissociation pressure and temperature of RuO2 bond proposed by Brunetti et al. 2. Since the dissociation pressure of RuO2 bond at 800oC is ~0.255Pa, which is much higher (~40 times) than the pressure of our vacuum annealing, RuOx reduces to Ru. On the other hand, with Ar annealing at the pressure of 101.3kPa, which is more than 5 orders of magnitude higher than the dissociation pressure of RuO2 bond, only RuO2 phases are formed and no Ru phase is observed. Since Ar is a noble gas, the oxidation of RuOx to RuO2 with Ar annealing and the reduction of RuOx to Ru with vacuum annealing (at the temperature of 800oC) are most likely due to the difference in the annealing pressure. In addition, with N2 annealing at the same pressure and temperature as Ar annealing, the I-V characteristic and XRD spectrum are similar to those of Ar annealed sample (see Figure 1). Hence, N2 does not seem to react with RuOx and only pressure plays a critical role in the formation of RuO2 in RuOx annealed at 800oC. In conclusion, based on our studies, the electrical and material characteristic differences observed in RuOx RuOx Schottky diodes annealed in N2, Ar and vacuum are most likely due to the annealing pressure and not the annealing ambient.

Effects of Annealing Pressure and Ambient on Thermally Robust RuOx Schottky Contacts on InAlN/AlN/GaN-on-Si(111) Heterostructure

We study the effects of annealing ambient and pressure (vacuum at the pressure of 6.67×10-3 Pa, N2 and Ar at the pressure of 101.3 kPa) on the electrical and material characteristics of RuOx Schottky diodes. With annealing in vacuum at 800 oC for 1 minute, the effective SBH of RuOx Schottky contacts decreases by ~0.208 eV and the reverse leakage current increases by about one order of magnitude with respect to those of contacts without annealing. In contrast, with annealing in Ar, the SBH increases by ~0.207 eV and the reverse leakage current decreases by about 100 times. Annealing in N2 yields the same results as annealing in Ar, and this indicates that N2 is unlikely to react with RuOx and the annealing pressure plays a critical role for the changes in the electrical and material characteristics of RuOx Schottky diodes.

100 MeV Si7+ Ion Irradiation Induced Modifications in Electrical Characteristics of Si Photo Detector: An In-Situ Reliability Study

The influence of 100 MeV Silicon (Si) ion irradiation on electrical characteristics of Si photo detectors has been analyzed using in-situ current-voltage characterization (I-V) in dark condition. The irradiation was performed over a wide range of fluences from 1×1011 ions/cm2 to 1×1013 ions/cm2. Key electrical parameters such as ideality factor (n), series resistance (Rs) and reverse bias leakage current (IR) for each irradiation fluence have been extracted from the I-V characteristics. The ideality factor of the unirradiated detector is found to be 1.48 and it gradually increased up to the fluence of 5×1011 ions/cm2, then it saturates around 3.4-3.5 for higher fluences. The I-V characteristics showed significant increase in forward bias and drastic increase in reverse leakage current. The value of IR is 7.23 nA for unirradiated detector and it increases about four orders of magnitude up to 5×1011 ions/cm2. Further there is no observable change in the value of IR. However the value of Rs increases initially and slightly decrease at higher fluences. The observed results are interpreted in terms of energy loss mechanisms of swift heavy ion as it passes through the different layers of the detector. The radiation induced defects in the bulk region and activation of multiple current transport mechanisms have attributed to the observed deviations in the electrical behaviour of the device. SRIM (Stopping power and Range of Ion in Matter) and TRIM (Transport and Range of Ion in Matter) simulation results of damage induced in the device have been reported in the present study. Linear energy transfer (LET), non ionizing energy loss (NIEL) damage contributions, total ionization dose (TID) and displacement damage dose (Dd) has been correlated with the observed degradation. Quantitative estimation of radiation hardness of the Si photo detector is done by comparing with the equivalent damage created by the proton at similar penetration depth in the present device structure.

Effects of high temperature annealing on single crystal ZnO and ZnO devices

We have systematically investigated the effects of high-temperature annealing on ZnO and ZnO devices using current voltage, deep level transient spectroscopy (DLTS) and Laplace DLTS measurements. Current–voltage measurements reveal the decrease in the quality of devices fabricated on the annealed samples, with the high-temperature annealed samples yielding devices with low barrier heights and high reverse currents. DLTS results indicate the presence of three prominent defects in the as-received samples. Annealing the ZnO samples at 300 °C, 500 °C, and 600 °C in Ar results in an increase in reverse leakage current of the Schottky contacts and an introduction of a new broad peak. After 700 °C annealing, the broad peak is no longer present, but a new defect with an activation enthalpy of 0.18 eV is observed. Further annealing of the samples in oxygen after Ar annealing causes an increase in intensity of the broad peak. High-resolution Laplace DLTS has been successfully employed to resolve the closely spaced energy levels.

Investigations on the nonidealities in Pd/n-GaN Schottky diodes grown by MOCVD

The effect of ammonia flow rate on the device characteristics of Pd/n-GaN Schottky diodes is discussed. The carrier concentration and hall mobility of the as grown epilayers were found to decrease with an increase in the V/III ratio. Current–Voltage ( I– V) barrier height initially decreases and then increases with an increase in V/III ratio. The ideality factor and leakage current decreases with an increase in the V/III ratio. The Capacitance–Voltage ( C– V) measurements of small area contacts showed a large variation in the slope of the lines of A 2/ C 2 vs. V plot. I– V– T measurements revealed that the ideality factor and the reverse leakage current increases with temperature confirming that the conduction mechanism is through trap-assisted tunneling process or deep center hopping conduction. Device parameters of GaN Schottky diodes were found to be strongly affected by the variation in localized structural changes induced by V/III ratio.

Leakage current origins and passivation effect of GaN-based light emitting diodes fabricated with Ag p-contacts

The origins of leakage currents and passivation effects of GaN-based light emitting diodes fabricated with Ag p-contacts have been investigated by electrical measurements. A significant increase in reverse leakage current is attributed to the surface migration of Ag. A passivation of mesa sidewalls by SiO2 is found to be effective in suppressing the reverse leakage. However, the passivation results in a somewhat increase in the forward leakage at moderate voltages. Such forward leakage is explained in terms of the presence of local deep-level states in p-GaN generated during SiO2 deposition, acting as a parasitic diode with a lower barrier height.

Charge collection degradation in relaxation semiconductor detectors fabricated from silicon

Silicon detectors damaged by 1 MeV neutrons show relaxation behaviour and demonstrate reduced charge collection efficiency (cce). Both effects occur as a result of the presence of radiation-induced defects in the forbidden gap. These defects act as generation-recombination centres in the former case, and as trapping centres in the latter. In particular, the shallow acceptor situated at 170 meV and detected at high fluences is implicated in the degradation of cce and also in the increase in reverse leakage current. The cce has been measured in a silicon detector irradiated such that it just type inverts and it is demonstrated to have degraded only slightly but it improves with increased reverse bias.

High-density plasma-induced etch damage of wafer-bonded AlGaInP/mirror/Si light-emitting diodes

Dry etch of wafer-bonded AlGaInP/mirror/Si light-emitting diodes (LEDs) with planar electrodes was performed by high-density plasma using an inductively coupled plasma (ICP) etcher. The etching characteristics were investigated by varying process parameters such as Cl2/N2 gas combination, chamber pressure, ICP power and substrate-bias power. The corresponding plasma properties (ion flux and dc bias), in situ measured by a Langmuir probe, show a strong relationship to the etch results. With a moderate etch rate of 1.3 μm/min, a near vertical and smooth sidewall profile can be achieved under a Cl2/(Cl2+N2) gas mixture of 0.5, ICP power of 800 W, substrate-bias power of 100 W, and chamber pressure of 0.67 Pa. Quantitative analysis of the plasma-induced damage was attempted to provide a means to study the mechanism of leakage current and brightness with various dc bias voltages (−110 to −328 V) and plasma duration (3–5 min) on the wafer-bonded LEDs. It is found that the reverse leakage current increases and the brightness decreases rapidly as the dc bias increases, which is a clear indication of severe damage accumulation in the sidewall. However, once a low-etch-rate condition (long duration of plasma treatment) is chosen to facilitate smooth sidewall and profile, the accumulated charge on the etched surface may not have enough time to relieve and make the leakage current increase. Finally, an effective recovery method is developed, where the plasma-induced damage can be partially restored after rapid thermal annealing at 450 °C in N2 ambience.

Characterization of the Co-Silicide Penetration Depth into the Junction Area for 0.15 and Sub-0.15 Micron CMOS Technology

The penetration depth of cobalt silicide layer in shallow junction is assessed using the current–voltage curve both in reverse and forward bias regions. The reverse leakage current characteristics said that silicide has affected both of the areal and peripheral intensive n+/p diodes because the leakage current is increased about one order of magnitude by silicidation. In case of p+/n junction, there is no increase of reverse leakage current. In case of forward region, however, only the forward current of peripheral intensive diode was increased by silicidation. From the different junction current behavior in forward and reverse bias region, it can be said that the penetrated depth of silicide layer is almost near to the space charge region but not into it for area diode. However, in case of peripheral intensive diode, silicide has penetrated into the space charge region. The Schottky contact area formed by silicide penetration is extracted as 3.02 µm2. The extracted Schottky barrier for n+/p parameter diode is 0.63 eV which is quite similar to the theoretical value of 0.64 eV.

Studies on the proton irradiation induced defects on Ni/n-GaAs Schottky barrier diodes

Ni/n-GaAs Schottky barrier diodes (SBDs) have been irradiated using low energy proton ions of fluences 1×10 14, 1×10 15 and 1×10 16 cm −2 to study the effect of irradiation damages very close to the interface. Current–voltage ( I– V) and capacitance–voltage ( C– V) characteristics of control and irradiated diodes have been carried out. The change in the reverse leakage current increases with increasing ion fluences. The barrier height of the SBDs has been found to decrease and the ideality factor deviates from the ideal behavior with increasing ion fluences. This non-rectifying behavior is due to the irradiation induced defects at the interface. The rectifying behavior of the SBDs improved, upon annealing at 573 and 673 K. The capacitance value of the irradiated diodes has been found to be less than the control diodes and it increases with increasing ion fluences. The capacitance of the irradiated and annealed diode decreases for all fluences due to the removal of the irradiation induced defects in the depletion region. The carrier concentration reduces by the proton irradiation through the mechanism of passivation and defects trapping at the interface and within in the depletion region. The time resolved luminescence spectrum in proton irradiated GaAs has been carried out in order to measure the life times of the photo excited carriers as a function of fluence. It is observed the carrier lifetimes decrease with increasing fluences.