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Electrical Characterization of GaN Based Ultraviolet and Blue Light Emitting Diodes

Published online by Cambridge University Press:  01 February 2011

Alphonse-Marie Kamto Tegueu ,
Okechukwu Akpa ,
Arindra Guha  and
Kalyankumar Das
Alphonse-Marie Kamto Tegueu
Affiliation:
[email protected], University of Arkansas, Electrical Engineering, 1343 N. Leverett Ave Apt 12, Fayetteville, AR, 72703, United States, (479)-587-9441
Okechukwu Akpa
Affiliation:
[email protected], Tuskegee University, Electrical Engineering, Tuskegee, AL, 36088, United States
Arindra Guha
Affiliation:
[email protected], Tuskegee University, Electrical Engineering, Tuskegee, AL, 36088, United States
Kalyankumar Das
Affiliation:
[email protected], Tuskegee University, Electrical Engineering, Tuskegee, AL, 36088, United States
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Abstract

Gallium 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.

Keywords

defectsIII-Vmicroelectronics
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 955: Symposium I – Advances in III-V Nitride Semiconductor Materials and Devices , 2006 , 0955-I07-05
Copyright
Copyright © Materials Research Society 2007

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