Effect of dislocations on green electroluminescence efficiency in GaP grown by liquid phase epitaxy

Abstract

The origins of dislocations in GaP grown by liquid phase epitaxy (LPE) and their effects upon green electroluminescence (EL) efficiency have been investigated by chemical etch pitting and scanning electron microscopy. Under normal growth conditions, the dislocation etch pit density (Pn) and configuration in the epitaxial layers are controlled by, and are approximately the same as, that in the liquid encapsulated Czochralski substrate. All dislocations which are revealed by chemical etching in the p LPE layer cause a localized reduction in luminescence. The dislocations are shown to behave as regions of rapid (nonradiative) recombination. Typically, reductions of a factor of -2 in green EL efficiency occur when Pn for the LPE layers is in the -2-5 X 10 5 cm-2 range, corresponding to an average separation of about two to four diffusion lengths in this material. The experimental results are supported by a simple theoretical model for the effects of dislocations on EL efficiency. These considerations explain why dislocations in GaP LPE layers for red light-emitting diodes (LED's), in contrast to green LED's, typically have no significant effect on EL efficiency since diffusion lengths are much shorter in the red LED's. PACS numbers: 78.60.F, 85.6O.J, 61.70.M [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 128.82.252.58 On: Tue

Acoustic-stimulated relaxation of GaAs1–хPх LEDs electroluminescence intensity

“…1). Relaxation process is accompanied by an increased efficiency of radiative recombination, apparently as a result of the restructuring of excited by US complex structure defects, the absorption of point defects by moving dislocations in the crystal regions between DDL and DDS, diffusion of simple defects to sewages, and because of changes in the charge state of non-radiative recombination centers, localized within these large-scale defects [14].…”

“…The authors [14] studied the dislocation effect on effectiveness of green luminescence in GaP. According to [14], the relative change in radiation efficiency η/η 0 as a function of dislocation density is …”

“…According to [14], the relative change in radiation efficiency η/η 0 as a function of dislocation density is …”

“…Therefore, it is likely that long-term relaxation of luminescence previously subjected to ultrasound GaAs 1-х P х LED is caused by the GaP sublattice, in which ultrasound-stimulated motion of dislocations causes the appearing of dislocation networks responsible for formation of "defects of dark lines" (DDL) and "defects of dark spots" (DDS) with a high non-radiative centers concentration. Accumulation of this type defects in the crystal is a natural consequence of the process of acousto-defective interaction, when the maximum loss of ultrasound wave energy is within the area of dislocation vibration [5,[13][14][15], which causes its release and subsequent movement to the formed before clusters -dislocation networks.…”

“…Ultrasonic (US) treatment of different industrial products and semiconductor devices is an effective tool of nondestructive influence on physical properties of materials in order to correct their characteristics in the right direction [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. For example, the use of ultrasound during crystal growth homogenizes melt ingots and gives a larger volume, improves film adhesion to silicon and metal substrates [2,3].…”