Electrical Characterization of Defects Introduced During Sputter Deposition of Schottky Contacts on n-type Ge (original) (raw)
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Materials Science in Semiconductor Processing, 2018
We have studied the defects introduced in n-type 4H-SiC during sputter deposition of tungsten using deep-level transient spectroscopy (DLTS). Current-voltage and capacitancevoltage measurements showed a deterioration of diode thermionic emission characteristics due to the sputter deposition. Two electrically active defects E 0.29 and E 0.69 were introduced. Depth profiling revealed that sputter deposition increases the concentration of the native Z 1 defect. A comparison with prominent irradiation and process induced defects showed that the E 0.29 was unique and introduced during sputter deposition only. The E 0.69 may be silicon vacancy related defect.
Materials Science in Semiconductor Processing, 2016
We have studied the defects introduced in n-type 4H-SiC during electron beam deposition (EBD) of tungsten by deep-level transient spectroscopy (DLTS). The results from currentvoltage and capacitance-voltage measurements showed deviations from ideality due to damage, but were still well suited to a DLTS study. We compared the electrical properties of six electrically active defects observed in EBD Schottky barrier diodes with those introduced in resistively evaporated material on the same material, as-grown, as well as after high energy electron irradiation (HEEI). We observed that EBD introduced two electrically active defects with energies E C-0.42 and E C-0.70 eV in the 4H-SiC at and near the interface with the tungsten. The defects introduced by EBD had properties similar to defect attributed to the silicon or carbon vacancy, introduced during HEEI of 4H-SiC. EBD was also responsible for the increase in concentration of a defect attributed to nitrogen impurities (E C-0.10) as well as a defect linked to the carbon vacancy (E C-0.67). Annealing at 400 °C in Ar ambient removed these two defects introduced during the EBD.
We have investigated by deep level transient spectroscopy the hole and electron trap defects introduced in n-type Ge during electron beam deposition ͑EBD͒ of Pd Schottky contacts. We have also compared the properties of these defects with those introduced in the same material during high-energy electron irradiation. Our results show that EBD introduces several electron and hole traps at and near the surface of Ge. The main defect introduced during EBD has electronic properties similar to those of the V-Sb complex, or E center, introduced during high-energy particle irradiation of Ge. This defect has two levels E 0.38 and H 0.30 that correspond to its ͑ϪϪ,Ϫ͒ and ͑Ϫ,0͒ charge states.
Electrical characterization of process- and radiation-induced defects in 4H-SiC
2016
Devices for operation in aerospace, manufacturing industries, defence and radiationharsh environments need to be manufactured from materials that are resistant to the frequent damage caused by irradiation and high-temperature environments. Silicon carbide (SiC) is a wide-bandgap semiconductor material that promises to provide solutions to these problems based on its capability to operate under extreme conditions of temperature and radiation. These conditions introduce defects in the materials. Such defects play an important role in determining the properties of devices, albeit beneficial or detrimental. Therefore it is very important to characterize the defects present in asgrown material as well as defects introduced during processing and irradiation. In this research, resistive evaporation (RE) as well as electron-beam deposition was employed for the fabrication of ohmic and Schottky barrier contacts on nitrogen-doped, n-type 4H-SiC substrate. The quality of the Schottky barrier d...
Materials Science in Semiconductor Processing, 2015
The influence of high energy electron (HEE) irradiation from a Sr-90 radio-nuclide on ntype Ni/4H-SiC samples of doping density 7.1 Â 10 15 cm À 3 has been investigated over the temperature range 40-300 K. Current-voltage (I-V), capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) were used to characterize the devices before and after irradiation at a fluence of 6 Â 10 14 electrons-cm À 2 . For both devices, the I-V characteristics were well described by thermionic emission (TE) in the temperature range 120-300 K, but deviated from TE theory at temperature below 120 K. The current flowing through the interface at a bias of 2.0 V from pure thermionic emission to thermionic field emission within the depletion region with the free carrier concentrations of the devices decreased from 7.8 Â 10 15 to 6.8 Â 10 15 cm À 3 after HEE irradiation. The modified Richardson constants were determined from the Gaussian distribution of the barrier height across the contact and found to be 133 and 163 A cm À 2 K À 2 for as-deposited and irradiated diodes, respectively. Three new defects with energies 0.22, 0.40 and 0.71 eV appeared after HEE irradiation. Richardson constants were significantly less than the theoretical value which was ascribed to a small active device area.
Journal of Applied Physics, 2014
Spectroscopic performance of Schottky barrier alpha particle detectors fabricated on 50 lm thick n-type 4H-SiC epitaxial layers containing Z 1/2 , EH 5 , and Ci1 deep levels were investigated. The device performance was evaluated on the basis of junction current/capacitance characterization and alpha pulse-height spectroscopy. Capacitance mode deep level transient spectroscopy revealed the presence of the above-mentioned deep levels along with two shallow level defects related to titanium impurities (Ti(h) and Ti(c)) and an unidentified deep electron trap located at 2.4 eV below the conduction band minimum, which is being reported for the first time. The concentration of the lifetime killer Z 1/2 defects was found to be 1.7 Â 10 13 cm À3. The charge transport and collection efficiency results obtained from the alpha particle pulse-height spectroscopy were interpreted using a drift-diffusion charge transport model. Based on these investigations, the physics behind the correlation of the detector properties viz., energy resolution and charge collection efficiency, the junction properties like uniformity in barrier-height, leakage current, and effective doping concentration, and the presence of defects has been discussed in details. The studies also revealed that the dominating contribution to the charge collection efficiency was due to the diffusion of charge carriers generated in the neutral region of the detector. The 10 mm 2 large area detectors demonstrated an impressive energy resolution of 1.8% for 5486 keV alpha particles at an optimized operating reverse bias of 130 V. V
Electrical characterization of electron irradiated and annealed lowly-doped 4H-SiC
Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms, 2017
The effect of high energy electron (HEE) irradiation on nickel Schottky contacts fabricated on lowly-doped n-type 4H-SiC was investigated by deep level transient spectroscopy (DLTS) and high resolution Laplace-DLTS. The Schottky contacts were deposited by resistive evaporation of nickel and were observed to be of good rectification quality from currentvoltage measurements. DLTS was performed up to 350 K to investigate the presence of defects before and after HEE irradiation. HEE irradiation was observed to induce three deep level defects below 350 K at 0.42 eV, 0.62 eV and 0.76 eV below the conduction band minimum. These deep level defects are labelled E 0.42 , E 0.62 and E 0.76. Defects E 0.42 and E 0.76 were observed after the same electron fluence and were annealed out at the same temperature, suggesting that the defects could be strongly related. The effect of HEE irradiation and annealing on as-grown defects was also investigated and is reported.
Correlation between Leakage Current and Ion-Irradiation Induced Defects in 4H-SiC Schottky Diodes
Materials Science Forum, 2006
The defects formation in ion-irradiated 4H-SiC was investigated and correlated with the electrical properties of Schottky diodes. The diodes were irradiated with 1 MeV Si+-ions, at fluences ranging between 1×109cm-2 and 1.8×1013cm-2. After irradiation, the current-voltage characteristics of the diodes showed an increase of the leakage current with increasing ion fluence. The reverse I-V characteristics of the irradiated diodes monitored as a function of the temperature showed an Arrhenius dependence of the leakage, with an activation energy of 0.64 eV. Deep level transient spectroscopy (DLTS) allowed to demonstrate that the Z1/Z2 center of 4H-SiC is the dominant defect in the increase of the leakage current in the irradiated material.