621.315.592, 621.383; PACS 85.60.Y

Electrophysical characteristics of LEDs based on GaN epitaxial films

P. Ph. Oleksenko, G. A. Sukach, P. S. Smertenko,
S. I. Vlaskina, A. B. Bogoslovskaya, I. O. Spichak

Institute of Semiconductor Physics, NAS Ukraine, 45 prospekt Nauki, Kyiv, 252028, Ukraine
Tel.380(44)2656477; Fax 380(44)2658342; E-mail:smertenk@class.semicond.kiev.ua
D. H. Shin
Dongguk University, Chung-ku, Pildong 3-26, Seoul,South Korea,
tel. 82 2 278 3429; fax. 82 2 278 4519; e-mail shin0313@chollian.dacom.co.kr

Abstract. Forward and reverse current-voltage (I-V) characteristics of light emitting diodes based on GaN epitaxial films were investigated by differential spectroscopy. This technique is based on calculating the differential slope of the I-V curve in the log-log scale in the following form: a = d lg i/d lg V and g = d lg a/d lg V. The main peculiarity of reverse I-V curves is the absence of rectification. The I(V) dependence can be approximated as i~V3 at low bias and i~V4 at high bias. These functions correspond to a high and superhigh level of double injection of current carriers, respectively. The forward current depends on voltage exponentially, with the ideality factor ranging from 6 to 8 under the bias of up to 1.5 V. The a(V) dependence has two maxima corresponding to a change of the charge flow mechanism from carrier diffusion to the field mechanism in the first case and to overcoming the recombination barrier in the second case. The second maximum is followed by light emission. Behavior of the I-V curves in temperature range from 150 K to 400 K is discussed and compared to that of spectral, kinetic, and power-current characteristics measured in the same temperature range.

Keywords: gallium nitride, light emission, current-voltage characteristic, double injection

Paper received 10.09.98; revised manuscript received 14.10.98; accepted for publication 28.10.98.

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