ISSN 1063-7850, Technical Physics Letters, 2007, Vol. 33, No. 2, pp. 143–146. © Pleiades Publishing, Ltd., 2007. Original Russian Text © D.V. Davydov, A.L. Zakgeim, F.M. Snegov, M.M. Sobolev, A.E. Chernyakov, A.S. Usikov, N.M. Shmidt, 2007, published in Pis’ma v Zhurnal Tekhnicheskoœ Fiziki, 2007, Vol. 33, No. 4, pp. 11–18. 143 Despite rapid progress in the technology of blue light-emitting diodes (LEDs) based on the InGaN/GaN system, many physical processes controlling the main properties of LEDs such as the parameters of radiative and nonradiative recombination, the quantum effi- ciency degradation, and the behavior of a system of extended defects (SED)—in particular, a high density of dislocations, a mosaic (domain) structure, and the influence of this system on the parameters of LEDs— still remain unclear. This situation hinders the further development of blue LEDs and the creation of effective LEDs operating in the green and ultraviolet spectral regions. In order to elucidate the influence of SED features on the properties of LEDs, we have used the deep-level transient spectroscopy (DLTS) technique to study the parameters of traps localized in the active region of LEDs of two types, which were manufactured in the same technological cycle using n + -GaN epilayers grown with the same level of doping, but in differing regimes. The active regions of LEDs comprised five InGaN/GaN quantum wells (QWs) with a commonly accepted layer thickness ratio (3 nm/12 nm) and a p + -GaN layer grown by means of metalorganic vapor- phase epitaxy. The LEDs of two types differed in the character of the structural organization of SED: the samples of type A had a well-ordered mosaic structure with predomi- nantly coherent domain matching (see [1–4]) via the formation of dilatation-type boundaries. The LEDs of type B had a less ordered mosaic structure that resulted in a greater density of dislocated walls on the bound- aries of poorly matched mosaic-structure domains. The LEDs of two types exhibited significantly different quantum efficiencies (η) and the values of both forward and reverse currents (I) at a bias voltage (U) below 1 V (Fig. 1): for type A, η = 18% at I = 1 mA; for type B, η was 2–3% at I = 1 mA and reached 10% at currents above 10 mA. The DLTS curves of deep traps in the active regions of LEDs were measured using a DL4600 spectrometer Localized States in the Active Region of Blue LEDs Related to a System of Extended Defects D. V. Davydov, A. L. Zakgeim, F. M. Snegov, M. M. Sobolev, A. E. Chernyakov, A. S. Usikov, and N. M. Shmidt* Ioffe Physicotechnical Institute, Russian Academy of Sciences, St. Petersburg, 194021 Russia * e-mail: Natalia.Shmidt@mail.ioffe.ru Received August 8, 2006 Abstract—Blue light-emitting diodes (LEDs) based on InGaN/GaN quantum wells (QWs) with different char- acters of the system of extended defects (SEDs) threading through the active region have been studied using the current–voltage (I–U), capacitance–voltage (C–V), and deep-level transient spectroscopy (DLTS) measure- ments in the dark and under illumination with white light in a temperature range from 100 to 450 K. The DLTS curves exhibit broad E1 and E2 peaks with amplitudes dependent on the illumination. This behavior can be explained assuming the presence of localized states related to SEDs in the active region of the LED. The LEDs with more developed SEDs are characterized by a greater concentration of donor-type traps, which leads to an increase in the density of free charge carriers in QWs, which screen the electron–hole interaction. This circum- stance can be among the factors responsible for a severalfold decrease in the quantum efficiency of such LEDs. PACS numbers: 85.60.Jb DOI: 10.1134/S1063785007020150 2 1 0 U, V 1E–7 1E–8 1E–9 1E–10 1E–11 I, A 1 2 3 4 Fig. 1. Current–voltage (I–U) curves of InGaN/GaN-based LEDs of (1, 2) type B and (3, 4) type A: (1, 3) forward branches; (2. 4) reverse branches.