Electrical Characterization of GaN Based Ultraviolet and Blue Light Emitting Diodes

2006 ◽  
Vol 955 ◽  
Author(s):  
Alphonse-Marie Kamto Tegueu ◽  
Okechukwu Akpa ◽  
Arindra Guha ◽  
Kalyankumar Das
Keyword(s):  
Light Emitting Diodes ◽  
Deep Level ◽  
Electrical Characterization ◽  
High Concentration ◽  
Light Emitting ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Double Heterojunction ◽  
Uv Leds

ABSTRACTGallium nitride based ultraviolet (UV) and blue AlGaN/GaN/AlGaN double heterojunction structure light emitting diodes (LEDs) were electrically characterized using current-voltage (I-V) and capacitance-voltage (C-V) measurements as a function of frequency. An analysis of logarithmic plots of the forward I-V characteristics indicated that current in these diodes was proportional to Vx, as opposed to eqV/nkT, where x was observed to be either 1 or 2 at low biases increasing to as high as 40 at higher biases. The dependence of diode forward current on Vx is likely to be due to space charge limited current in the presence of a high concentration of deep level states in the bandgap. The concentration of deep states and their position in the band gap were extracted from these logarithmic plots. For both the blue and the UV LEDs, several closely spaced levels were obtained, located most likely in the range between EV and EV + 0.5 eV with concentrations of the order of 1016/cm3 to 1017/cm3. Capacitance-voltage measurements as a function of frequency (200 Hz - 1 MHz) at room temperature yielded a density of approximately 1 × 1015 cm−3 located at 0.46 eV above the valence band-edge for both the UV and blue LED. Even though the location of these deep states from the I-V and C-V measurements are within the same range, the two orders magnitude difference in the concentration of deep states is not well understood at this point.

Electrical Measurement of Recombination Lifetime in Blue Light Emitting Diodes

2004 ◽  
Vol 829 ◽  
Author(s):  
M. A. Awaah ◽  
R. Nana ◽  
K. Das
Keyword(s):  
Blue Light ◽  
Light Emitting Diodes ◽  
Deep Level ◽  
Electrical Measurement ◽  
High Concentration ◽  
Recombination Lifetime ◽  
Light Emitting ◽  
Radiative Processes ◽  
Current Voltage ◽  
Capacitance Voltage

ABSTRACTA recombination lifetime of approximately 25 ns was extracted from measured reverse recovery storage times in AlGaN/GaN/AlGaN double heterojunction blue light emitting diodes. This experimentally determined lifetime is expected to arise from a combination of radiative and non-radiative processes occurring in the diodes. The non-radiative processes are likely to be due the presence of a high concentration deep-states as identified from the current-voltage and capacitance-voltage measurements. Current-voltage characteristics of these diodes were highly non-ideal as indicated by high values of the ideality factor ranging from 3.0 – 7.0. Logarithmic plots of the forward characteristics indicated a space-charge-limited-current (SCLC) conduction in presence of a high density of “deep-level states” in the active region of the diodes. An analysis of these characteristics yielded an approximate density of these deep-level states as 2 × 1017/cm3. The density of deep-states extracted from capacitance-voltage measurements were in good agreement with that obtained from current-voltage measurements.

Electrical Characterization of Blue Light Emitting Diodes as a Function of Temperature

2005 ◽  
Vol 892 ◽  
Author(s):  
Murthy Madhu ◽  
Alphonse Marie Kamto Tegueu ◽  
Michael Awaah ◽  
Dake Wang ◽  
Minseo Park ◽  
...  
Keyword(s):  
Blue Light ◽  
Light Emitting Diodes ◽  
Electrical Characterization ◽  
Leakage Currents ◽  
Light Emitting ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Double Heterojunction ◽  
Increasing Temperature ◽  
Recombination Lifetimes

AbstractBlue light emitting diodes (LEDs) based on an AlGaN/GaN/AlGaN double heterojunction structure were electrically characterized as a function of temperature. Current-voltage (I-V), capacitance-voltage (C-V) and reverse recovery storage time measurements were conducted at temperatures in the range between -8° and 75° C. Capacitance-voltage measurements as a function frequency (20 Hz – 1 MHz) and electroluminescence study at room temperature were also performed. It was observed that the diode turn-on voltage decreased with increasing temperature, however, reverse leakage currents monitored at -1, -5 and -10 V showed only a slight increase with increasing temperature. The concentration of deep states and their position in the bandgap, as extracted from logarithmic plots of the forward characteristics, were not influenced by the measurement temperature. Recombination lifetimes, as obtained from experimentally determined reverse recovery storage times, remained constant over the range of temperature considered. A higher value of diode capacitance was observed at low measurement frequencies (20 Hz – 1 kHz), gradually dropping to a lower value over a frequency range between (1 kHz – 100 kHz) and remained constant from 100 kHz to 1 MHz. A loss peak centered about 10 kHz was observed in the corresponding plot of gm/ω as a function of frequency, f. The position of the peak in the gm/ω - frequency (f) plot and dC/dω(for f in the range 1 kHz – 100 kHz ), yielded a concentration of deep-states of approximately 2.2 × 1015/cm3, located at 0.39 eV above the valence bandedge.

Electrical characterization of organic light-emitting diodes using dipotassium phthalate as n-type dopant

2008 ◽  
Vol 93 (8) ◽  
pp. 083505 ◽  
Author(s):  
Meng-Huan Ho ◽  
Ming-Ta Hsieh ◽  
Teng-Ming Chen ◽  
Jenn-Fang Chen ◽  
Shiao-Wen Hwang ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Electrical Characterization ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light

Effect of deep-level states on current-voltage characteristics and electroluminescence of blue and UV light-emitting diodes

2010 ◽  
Vol 207 (6) ◽  
pp. 1489-1496 ◽  
Author(s):  
R. Nana ◽  
P. Gnanachchelvi ◽  
M. A. Awaah ◽  
M. H. Gowda ◽  
A. M. Kamto ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Deep Level ◽  
Uv Light ◽  
Light Emitting ◽  
Current Voltage ◽  
Current Voltage Characteristics

Electrical Characterization of In Schottky Contacts to Epitaxial n-In0.46Ga0.54P Grown on n+-GaAs by Mocvd

1996 ◽  
Vol 448 ◽  
Author(s):  
N. Marcano ◽  
A. Singh
Keyword(s):  
Barrier Height ◽  
Thermionic Emission ◽  
Electrical Characterization ◽  
Interface Layer ◽  
Zero Bias ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
Direct Current Voltage ◽  
Etched Surface

AbstractIn/n-In0.46Ga0.54P Schottky diode was fabricated by thermal evaporation of In on chemically etched surface of In0.45Ga0.54P:Si epitaxial layer grown on highly doped n type GaAs. The In metal formed a high quality rectifying contact to In0.46Ga0.54P:Si with a rectification ratio of 500. The direct current-voltage/temperature (I-V/T) characteristics were non-ideal with the values of the ideality factor (n) between 1.26-1.78 for 400>T>260 K. The forward I-V data strongly indicated that the current was controlled by the generation-recombination (GR) and thermionic emission (TE) mechanisms for temperature in the range 260-400 K. From the temperature variation of the TE reverse saturation current, the values of (0.75±0.05)V and the (4.5±0.5)×10-5 Acm-2K-2 for the zero bias zero temperature barrier height (φoo) and modified effective Richardson constant were obtained. The 1 MHz capacitance-voltage (C-V) data for 260 K < T < 400 K was analyzed in terms of the C-2-V relation including the effect of interface layer to obtain more realistic values of the barrier height (φbo). The temperature dependence of φbo was described the relation φbo =(0.86±10.03) - (8.4±0.7)×l0-4T. The values of φoo, obtained by the I-V and C-V techniques agreed well.

Electrical and Optical Characterisation of Homojjunction Gallium Nitride Light Emitting Diodes

1997 ◽  
Vol 482 ◽  
Author(s):  
G M Laws ◽  
J Morgan ◽  
G B Ren ◽  
I Harrison ◽  
E C Larkins ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Full Width Half Maximum ◽  
Light Emitting Diodes ◽  
Deep Level ◽  
Deep Level Emission ◽  
Near Band Edge ◽  
Band Edge Emission ◽  
Light Emitting ◽  
Current Voltage ◽  
Current Voltage Characteristics

AbstractWe report on the fabrication and characterisation gallium nitride light emitting diodes (LEDs) grown by molecular beam epitaxy on (0001) oriented sapphire and (111)B GaAs substrates. The current voltage characteristics of the devices grown on sapphire show turn on voltages of between 4 and 5V with large on-series resistance of 600Ω; for corresponding devices grown on GaAs these parameters are between 6 and 7V and 150 Ω, respectively.Room temperature electroluminescence (EL) spectra from the GaN LEDs ,grown on sapphire substrates, show a dominant emission at 3.2 eV (397nm) with a full width half maximum (FWHM) of 335 meV which is attributed to free electron to acceptor transitions (e, A−Mg). A broad low intensity deep level emission is also observed centred at 2.4 eV (506nm). The peak of the EL from the devices grown on GaAs is at 3.1eV rather than 3.2eV. The differences between the two sets of devices are probably caused by the different device geometry.Preliminary results show that an “annealing” effect caused by electrical stressing resulted in an improvement of the EL spectra. The stressed samples show an increase in the near band edge emission intensity, a 20meV reduction in the FWHM and a significant reduction in the intensity of the deep level emission. The devices have a large 1/f noise contribution which does not appear to change after electrical stressing.

Homoepitaxial growth and electrical characterization of GaN-based Schottky and light-emitting diodes

2007 ◽  
Vol 300 (2) ◽  
pp. 382-386 ◽  
Author(s):  
X.A. Cao ◽  
H. Lu ◽  
E.B. Kaminsky ◽  
S.D. Arthur ◽  
J.R. Grandusky ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Electrical Characterization ◽  
Light Emitting ◽  
Homoepitaxial Growth

Probing at Nanoscale Underneath the Gate Oxides in 4H-SiC MOS-Based Devices Annealed in N2O and POCl3

2014 ◽  
Vol 806 ◽  
pp. 143-147
Author(s):  
P. Fiorenza ◽  
Marilena Vivona ◽  
L.K. Swanson ◽  
Filippo Giannazzo ◽  
C. Bongiorno ◽  
...  
Keyword(s):  
Electrical Characterization ◽  
Cross Sectional ◽  
Direct Demonstration ◽  
Current Voltage ◽  
Capacitance Voltage ◽  
N Incorporation ◽  
The Impact ◽  
Post Deposition ◽  
Partial Compensation

In this paper a comparative study of the impact of N2O and POCl3 annealing on the SiO2/SiC system is presented, combining nanoscale electrical characterization of SiC surface doping by scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM) to the conventional capacitance-voltage (C-V) and current-voltage (I-V) measurements on MOS-based devices. A significant reduction of the interface states density (from 1.8×1012 to 5.7×1011 cm-2eV-1) and, correspondingly, an increase in the carrier mobility (from 19 to 108 cm2V-1s-1) was found moving from N2O to POCl3 annealing. Furthermore, SSRM measurements on bare p+-type SiC regions selectively exposed to N2O and POCl3 at high temperature provided the direct demonstration of the incorporation of N or P-related donors in the SiC surface, leading to a partial compensation of substrate acceptors during N2O treatment and to an overcompensation during POCl3 annealing. Finally, cross-sectional SCM profiles performed on epitaxial n-doped 4H-SiC with 45 nm SiO2 (subjected to post deposition annealing in the two ambients) allowed to quantify the active donors concentrations associated to P or N incorporation under the gate oxide, showing almost a factor of ten higher doping (4.5×1018cm-3 vs 5×1017cm-3) in the case of P related donors.

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