Browsing by Subject "Reverse bias"
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Item Open Access AlxGa1-xN-based avalanche photodiodes with high reproducible avalanche gain(2008) Tut, Turgut; Gökkavas, Mutlu; Özbay, EkmelWe report high performance solar-blind photodetectors with reproducible avalanche gain as high as 1570 under ultraviolet illumination. The solar-blind photodetectors have a sharp cut-off around 276 nm. The dark currents of the 40 μm diameter devices are measured to be lower than 8 femto-amperes for bias voltages up to 20 V. The responsivity of the photodetectors is 0.13 A/W at 272 nm under 20 V reverse bias. The thermally limited detectivity is calculated as D* = 1.4 × 1014 cm Hz1/2 W-1 for a 40 μm diameter device. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.Item Open Access Diode behavior in ultra-thin low temperature ALD grown zinc-oxide on silicon(AIP Publishing, 2013) El-Atab, N.; Alqatari, S.; Oruc F.B.; Souier, T.; Chiesa, M.; Okyay, Ali Kemal; Nayfeh, A.A thin-film ZnO(n)/Si(p+) heterojunction diode is demonstrated. The thin film ZnO layer is deposited by Atomic Layer Deposition (ALD) at different temperatures on a p-type silicon substrate. Atomic force microscopy (AFM) AC-in-Air method in addition to conductive AFM (CAFM) were used for the characterization of ZnO layer and to measure the current-voltage characteristics. Forward and reverse bias n-p diode behavior with good rectification properties is achieved. The diode with ZnO grown at 80°C exhibited the highest on/off ratio with a turn-on voltage (VON) ∼3.5 V. The measured breakdown voltage (VBR) and electric field (EBR) for this diode are 5.4 V and 3.86 MV/cm, respectively. © 2013 © 2013 Author(s).Item Open Access Electrical characterization of MS and MIS structures on AlGaN/AlN/GaN heterostructures(ELSEVIER, 2010) Arslan, E.; Bütün, S.; Şafak, Y.; Uslu, H.; Tascioglu I.; Altindal, S.; Özbay, EkmelThe forward and reverse bias I-V, C-V, and G/ω-V characteristics of (Ni/Au) Schottky barrier diodes (SBDs) on the Al 0.22Ga 0.78N/AlN/GaN high-electron-mobility-transistor (HEMTs) without and with SiN x insulator layer were measured at room temperature in order to investigate the effects of the insulator layer (SiN x) on the main electrical parameters such as the ideality factor (n), zero-bias barrier height ( B0), series resistance (R s), interface-state density (N ss). The energy density distribution profiles of the N ss were obtained from the forward bias I-V characteristics by taking into account the voltage dependence of the effective barrier height ( e) and ideality factor (n V) of devices. In addition, the N ss as a function of E c-E ss was determined from the low-high frequency capacitance methods. It was found that the values of N ss and R s in SBD HEMTs decreases with increasing insulator layer thickness.Item Open Access High-speed solar-blind AlGaN Schottky photodiodes(Cambridge University Press, 2003) Bıyıklı, Necmi; Kimukin, İbrahim; Kartaloğlu, Tolga; Aytür, Orhan; Özbay, EkmelWe report high-speed solar-blind AlGaN-based Schottky photodiodes. AlGaN/GaN heterostructure device layers were grown on sapphire substrate. The devices were fabricated on AlGaN/GaN heterostructuresusing a microwave compatible fabrication process. Schottky photodiodes with Au and indium-tin-oxide (ITO) Schottky contacts were fabricated. Current-voltage, spectral responsivity, and high-speed measurements were performed. Both Schottky samples exhibited very low sub-pA dark currents at high reverse bias. A bias dependent spectral responsivity was observed with a peak responsivity of 89 mA/W at 267 nm, and 44 mA/W at 263 nm for Au and ITO-Schottky devices respectively. Time-based high-frequency measurements at 267 nm resulted in pulse responses with rise times and pulse-widths as short as 13 ps and 74 ps respectively. The fastest solar-blind detector had a record 3-dB bandwidth of 1.10 GHz.Item Open Access Linear electro-optic coefficient in multilayer self-organized InAs quantum dot structures(IEEE, 2007) Akca, B. Imran; Dana, Aykutlu; Aydınlı, Atilla; Rossetti, M.; Li L.; Dagli, N.; Fiore, A.The electro-optic coefficients of self-organized InAs quantum dot layers in molecular beam epitaxy grown laser structures in reverse bias have been investigated. Enhanced electrooptic coefficients compared to bulk GaAs were observed. © 2003 Optical Society of America.Item Open Access On the profile of frequency and voltage dependent interface states and series resistance in (Ni/Au)/Al0.22Ga0.78N/AlN/GaN heterostructures by using current-voltage (I-V) and admittance spectroscopy methods(Elsevier, 2011-06-08) Demirezen, S.; Altindal, S.; Özelik, S.; Özbay, EkmelIn order to explain the experimental effect of interface states (N ss) and series resistance (Rs) of device on the non-ideal electrical characteristics, current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) characteristics of (Ni/Au)/Al 0.22Ga0.78N/AlN/GaN heterostructures were investigated at room temperature. Admittance measurements (C-V and G/ω-V) were carried out in frequency and bias voltage ranges of 2 kHz-2 MHz and (-5 V)-(+5 V), respectively. The voltage dependent Rs profile was determined from the I-V data. The increasing capacitance behavior with the decreasing frequency at low frequencies is a proof of the presence of interface states at metal/semiconductor (M/S) interface. At various bias voltages, the ac electrical conductivity (σac) is independent from frequencies up to 100 kHz, and above this frequency value it increases with the increasing frequency for each bias voltage. In addition, the high-frequency capacitance (C m) and conductance (Gm/ω) values measured under forward and reverse bias were corrected to minimize the effects of series resistance. The results indicate that the interfacial polarization can more easily occur at low frequencies. The distribution of Nss and R s is confirmed to have significant effect on non-ideal I-V, C-V and G/ω-V characteristics of (Ni/Au)/Al0.22Ga0.78N/AlN/ GaN heterostructures.Item Open Access Solar-blind AlGaN-based Schottky photodiodes with low noise and high detectivity(American Institute of Physics, 2002) Bıyıklı, Necmi; Aytur, O.; Kimukin, I.; Tut, T.; Özbay, EkmelWe report on the design, fabrication, and characterization of solar-blind Schottky photodiodes with low noise and high detectivity. The devices were fabricated on n-/n+ AlGaN/GaN heterostructures using a microwave compatible fabrication process. True solar-blind operation with a cutoff wavelength of ∼274nm was achieved with AlxGa1-xN (x=0.38) absorption layer. The solar-blind detectors exhibited <1.8nA/cm2 dark current density in the 0-25 V reverse bias regime, and a maximum quantum efficiency of 42% around 267 nm. The photovoltaic detectivity of the devices were in excess of 2.6×1012cmHz1/2/W, and the detector noise was 1/f limited with a noise power density less than 3×10-29A2/Hz at 10 kHz. © 2002 American Institute of Physics.Item Open Access Surface recombination noise in InAs / GaSb superlattice photodiodes(IOP Institute of Physics Publishing, 2013) Tansel, T.; Kutluer, K.; Muti, A.; Salihoglu, Ö.; Aydınlı, Atilla; Turan, R.The standard Schottky noise approach alone is not sufficient to describe the noise mechanism in an InAs/GaSb superlattice photodetector at reverse negative bias. The additional noise identified appears at surface activation energies below 60meV and is inversely proportional to the reverse bias. In order to satisfactorily explain the experimental data, we hereby propose the existence of a surface recombination noise that is a function of both the frequency and bias. The calculated noise characteristics indeed show good agreement with the experimental data.