Electron Traps in n-GaN Grown on Si (111) Substrates by MOVPE

Abstract

Deep level electron traps in n-GaN grown by metal organic vapor phase epitaxy (MOVPE) on Si (111) substrate were studied by means of deep level transient spectroscopy (DLTS). The growth of n-GaN on different pair number of AlN/GaN superlattice buffer layers (SLS) system and on c-face sapphire substrate are compared. Three deep electron traps labeled E2 (the energy level is not clear), E4 (0.7-0.8 eV), E5 (1.0-1.1 eV), were observed in n-GaN on Si substrate. And the concentrations of these traps observed for n-GaN on Si are very different from that observed for n-GaN on sapphire substrate. E4 is the dominant of these levels for n-GaN on Si substrate, and it is not related to linear array defect like dislocation line, but it behaves like point-defect based on the analysis by electron capture kinetics, in spite of having high dislocation density to the order of 10 10 cm -2 .

Donor and acceptor characteristics of native point defects in GaN

“…The activation energy of further ionisation N Ga (+1| + 2)e can be estimated to lie between 0.43 and 0.56 eV. It is unlikely that this process is responsible for the ubiquitous E c − 0.56 eV trap discussed above-we expect the antisite to be only a small minority defect, but it is consistent with the behaviour of rare ET8 traps at E c − 0.49 eV [126], which have previously been associated with N Ga, and show a barrier of about 0.15 eV for electron capture (see discussion in [120]). Finally, the hole capture by N +3 Ga at 1.71 eV is again consistent with the position of H5 traps [119], for which, however, we have already seen more candidates.…”

Deep traps in GaN-based structures as affecting the performance of GaN devices

“…ET8 traps at E c À(0.47-0.49) eV are sometimes reported for MOCVD grown undoped n-GaN [212]. The traps were observed to increase in concentration when moving inside the samples grown by epitaxial lateral overgrowth [213].…”

“…The traps were observed to increase in concentration when moving inside the samples grown by epitaxial lateral overgrowth [213]. They are the rare traps for which the normal, not logarithmic, dependence of the traps peak magnitude in DLTS was observed [212]. The capture of electrons to the traps required overcoming a relatively high barrier of about 0.15 eV so that the room temperature persistent photoconductivity in undoped n-GaN observed in many cases has been partly attributed to these traps [214].…”

Comparison of electrical properties in GaN grown on Si(111) and c-sapphire substrate by MOVPE

“…And net doping concentration of n-GaN on GaN substrates is studied in relation to dislocation density [6]. However, currently there are few reports available on study of the defects such as deep traps in GaN grown on Si substrates [7,8]. In this paper, we have examined electrical properties, especially net doping characteristics in n-GaN grown on Si(111), and c-sapphire substrates, clarified that crystal qualities, impurity concentrations and investigated the deep traps by means of DLTS measurement.…”