Photoluminescence from Be‐Doped GaN Grown by Metal‐Organic Chemical Vapor Deposition

Abstract

A systematic photoluminescence study of Be‐doped GaN grown by metal‐organic chemical vapor deposition is presented. All Be‐doped samples show the ultraviolet luminescence (UVLBe) band with a maximum at 3.38 eV and the yellow luminescence (YLBe) band with a maximum at ≈2.15 eV in GaN:Be having various concentrations of Be. The UVLBe band is attributed to the shallow state of the BeGa acceptor with a delocalized hole. The YLBe band is caused by a Be‐related defect, possibly the polaronic state of the BeGa acceptor with the charge transition level at 0.3 eV above the valence band. This broad band exhibits unusual properties. In particular, it always shows two steps in its thermal quenching. The second step at T ≈ 200 K is attributed to the emission of holes from the 0.3 eV level to the conduction band. The origin of the first step remains unexplained.

Photoluminescence from defects in GaN

“…1,11 Another dual-nature acceptor in GaN is the BeGa defect . 54 Recent experimental results indicate that the yellow band (YLBe) with a maximum at 2.15 eV in Be-doped GaN is caused by electron transitions via the deep state of the BeGa acceptor, 39 in agreement with theoretical predictions. 14,54 The UVLBe band with a maximum at 3.38 eV has been attributed to the shallow state of the BeGa acceptor.…”

“…50 Several versions of hybrid functionals are used to describe defects in GaN, and the results of the calculations are slightly different. 51,52 Figure 10 compares experimentally found positions of PL band maxima with those calculated by three groups -D. Demchenko (DD), 20,12,27,23,11,39 Van de Walle (VDW), 14,53 and Lany and Zunger (LZ). 54 A good agreement with the experiment has been achieved for the CN defect.…”

“…In Be-doped GaN layers grown by MBE or MOCVD (semi-insulating and conductive n-type), the quenching of the YLBe band begins at 180-200 K, in agreement with the estimated EA = 0.30 eV for the BeGa defect. 39 A similar yellow band in bulk GaN with high concentrations of Be and O is attributed to the BeGaON complex. 40 This yellow band is quenched only at T > 500 K, 41 which indicates that the related defect level is located at about 0.8 eV above the VBM.…”

Photoluminescence from GaN Implanted with Be and F

“…The shape of the YL Be band can be fit using Equation (1) with the same parameters (Table 2) as for the YL Be band in Be-doped GaN grown by MBE, MOCVD, and in Be-implanted GaN. [2,3,18,29] The band maximum in semi-insulating GaN samples red-shifts by up to 60 meV with decreasing P exc from 0.1 to 10 À5 W cm À2 . As in the case of Ca-implanted GaN, [30] the shift can be caused by local electric fields in semi-insulating GaN.…”

“…[2] The quantum efficiency of the YL Be band approaches unity in GaN:Be samples grown by metal-organic chemical vapor deposition (MOCVD). [2] Be-doped GaN samples grown by molecular beam epitaxy (MBE) also reveal a green band (GL2) with a maximum at 2.33 eV and a red band (RL Be ) with a maximum at 1.8 eV that are attributed to the nitrogen vacancy (V N ) and the V N Be Ga complex, respectively. [3] The attempts to produce conductive p-GaN:Be are rarely successful [4][5][6][7] and require confirmation.…”