A review of leakage current mechanism in nitride based light emitting diode

We review the dominant mechanism and characteristics which give rise to the existence of forward and reverse leakage current in nitride based light emitting diode (LED). The existence of leakage current can affect the reliability and efficiency of LED. Hence, to understand the mechanism that is responsible for its existence, the occurrence of leakage current is divided into three main parameters: 1) low bias; 2) medium or high bias; 3) temperature dependence. For reverse bias, many reports suggest Poole-Frenkel as the dominant mechanism in low reverse bias and some others suggested the field dependent tunneling mechanism. In high reverse bias, many studies have shown tunneling to be the dominant mechanism. However ,there is also few other papers suggesting variable range hopping (VRH) or PF being a dominant mechanism. When the reverse bias currentvoltage measurement below 200 K, majority studies reported VRH to be the dominant mechanism. Meanwhile, for forward bias, defect-assisted tunneling is most likely the dominant mechanism. At low forward voltages, electrons are believed to be the dominant carriers for defect assisted tunneling, while holes are reported to be likely the dominant carrier in medium forward voltages

Investigation of Multiwavelength Performance Based on Different SOAs

We investigated multiwavelength fiber laser (MWFL) performance using different types of semiconductor optical amplifiers (SOAs) utilizing Lyot filter as comb filter. The lasing performances of linear SOA (LSOA), nonlinear SOA (NLSOA) and booster optical amplifier (BOA) at different current settings were observed. Among the three SOAs, LSOA has the best lasing performance due to the lowest peak power difference with the highest number of lasing lines, a high ER value of 42 dB and considerable high peak power of -14.1 dBm at 550 mA. The multiwavelength laser is stable within 60 minutes at power fluctuation of less than 0.2 dB. The output spectra at 550 mA for all the SOAs are 70 nm to 80 nm wavelength difference from the ASE spectra

Effect of electron irradiation on the electrical and optical characteristics of gallium-nitride light emitting diodes

We study the effect of electron irradiation on the electrical and optical characteristics of commercial gallium-nitride light emitting diodes in the fluence region from 1015 to 1017 electrons/cm2. After electron irradiation, the forward leakage current shows no significant changes, while the reverse-leakage current increases twice under the fluence 9.90×1016 electrons/cm2. This suggests the existence of radiation damage-induced traps. The irradiation reduces the capacitance and the carrier concentration, which can be attributed to deactivation of dopant atoms. Basing on electroluminescence measurements, we prove that the luminescence intensity and the red shift of peak position increase significantly with increasing dose. The peak-wavelength shift can be attributed primarily to the radiation-induced defects that cause formation of red bands and, at the same time, gradually suppress the band-edge luminescence

Effect of polarization adjustment towards the performance of SOA-based multiwavelength fiber laser

We investigate the performance of multiwavelength fiber laser (MWFL) at six simultaneous angle settings of half wave plate (HWP) and quarter wave plate (QWP) using two different types of semiconductor optical amplifiers (SOAs): a booster amplifier and an in-line amplifier. In order to generate multiwavelength, a Lyot filter is inserted into the cavity to serve as a comb filter. MWFL using the booster optical amplifier (BOA) shows superior performance in terms of spectrum range, number of lasing lines, and extinction ratio (ER). The laser stability is excellent where all the output peaks experience a minor power fluctuation with maximum value of 0.28 dB within 100 min of observation time

Electrical characterization of commercial GaN LEDs subjected to electron radiation with different conveyor speed per pass

Commercially fabricated nitride-based light emitting diodes (LEDs) is of interest due to its attractive material properties of high temperature tolerance and breakdown strength, making it suitable to be used in extreme environment. Hence, our focus is on the electrical characterization of commercial Gallium Nitride (GaN) subjected to 1000kGy and 1500kGy dose of electron radiation with the conveyor speed were adjusted to 100kGy and 50kGy per pass. Capacitance-voltage (C-V) and current-voltage (I-V) characteristics of commercial GaN LEDs before and after radiation have been investigated. I-V measurement shows no presence of current and measurement of C-V shows no presence of capacitance after irradiated with both dose level at the conveyor speed of 100kGy per pass, indicating an open circuit problem. However, LEDs that were irradiated with the same amount of dose with a conveyor speed of 50kGy per pass shows an increase in reverse leakage curren

Capacitance-voltage characterization of commercial gallium nitride diodes subjected to electron radiation

The effects of electron radiation on commercially fabricated gallium nitride light emitting diodes (LEDs) is of interest due to its high tolerance against temperature and high breakdown voltage, making it suitable to be used in an extreme environment. LED based on this material is used as part of visible light communication and as an illuminating source in space. However, due to the presence of high energy electron in space, these LEDs are vulnerable towards electron radiation. Hence, this paper focus on the electrical characterization of commercial Gallium Nitride (GaN) LEDs subjected to electron radiation dose ranged from 1MGy to 10MGy. The devices that were used in this study are Kingbright GaN Blue LEDs (part #L-53MBC) and Vishay GaN Blue LEDs (part #TLHB5400). Capacitance-voltage (C-V) characteristics of commercial GaN LEDs before and after irradiation were investigated. As the radiation dose increase, the amount of capacitance and doping concentration decreases. This is believed due to deactivation of dopants atoms in the bulk

Radiation damage study of electrical properties in GaN LEDs diode after electron irradiation

Nitride-based light emitting diodes (LEDs) is an attractive material due to its high temperature tolerance and suitable to be used in extreme environment. The irradiation process of Gallium Nitride (GaN) diode was carried out by electron irradiation with 1000 kGy and 1500 kGy doses with a conveyor speed of 50 kGy per pass. Capacitance-voltage (C-V) and current-voltage (IV) characterization for both pre and post irradiation samples was done. Both current and capacitance show decreasing while reverse leakage current increased after irradiation. The reverse leakage current revealed that the current were start leakage at 1.0 x10-7 A and 1.0 x10-9 A for 1000 kGy and 1500 kGy irradiations respectively. The current-voltage graph indicated that the effect of electron irradiation on diode produced weak spots as defect cause leakage current. The traps and bulk defect is believed to contributed to the leakage current increased

Sensing texture using an artificial finger and a data analysis based on the standard deviation

The results from experiments with a screen-printed piezoelectric sensor, mounted on an artificial finger-tip and including a cosmetic covering, are shown to detect surface information from regular texture patterns. For the automatic control of an artificial hand and to feedback information to the amputee, an algorithm has been developed based on the standard deviation (SD) of signal data from the sensor. The SD analysis for texture detection is novel as it uses a combination of arithmetic processes. It windows the data sequentially and calculates the SD of the data in the windows and then averages the SDs. The output from the algorithm is the frequency spectrum of a signal. Plots, from the output of the algorithm, show events that correspond to the cyclic waveforms produced from the regularity of object surface patterns. The results from the algorithm are confirmed with an analysis of the signals using fast Fourier transforms

Effects of electron radiation on commercial power MOSFET with buck converter application

Microelectronic power converters such as buck and boost converter are required to be tolerant to radiations including electron radiation. This paper examines electron radiation effects on the I–V characteristics of VDMOSFET and its corresponding effects in buck converter. Analysis of the electrical characteristics shows that after irradiation the threshold voltage and drain current for all VDMOSFETs degraded more than two orders of magnitude. The impact of this electrical degradation has been investigated in an application of typical buck converter circuit. The buck converter with n-channel switching transistor shows that after irradiation its output voltage increased with the drain current in the n-channel ZVN4424A VDMOSFET, while the buck converter with p-channel switching transistor shows its output voltage decreased with the drain current in the p-channel ZVP4424A VDMOSFET after irradiation

Sensing texture using an artificial finger and a data analysis based on the standard deviation

The results from experiments with a screen-printed piezoelectric sensor, mounted on an 23 artificial finger-tip and including a cosmetic covering, are shown to detect surface information from 24 regular texture patterns. For the automatic control of an artificial hand and to feedback information to 25 the amputee, an algorithm has been developed based on the standard deviation of signal data from the 26 sensor. The standard deviation analysis for texture detection is novel as it uses a combination of 27 arithmetic processes. It windows the data sequentially and calculates the standard deviation of the data 28 in the windows and then averages the standard deviations. The output from the algorithm is the 29 frequency spectrum of a signal. Plots for the output from the algorithm show events that correspond to 30 the cyclic waveforms produced from the regularity of object surface patterns. The results from the 31 algorithm are confirmed with an analysis of the signals using Fast Fourier Transforms