A direct evidence of allocating yellow luminescence band in undoped GaN by two-wavelength excited photoluminescence

Abstract

The behavior of below-gap luminescence of undoped GaN grown by MOCVD has been studied by the scheme of two-wavelength-excited photoluminescence. The emission intensity of shallow donor to valence band transition (IOX) increased while intensities of donor-acceptor pair transition and the Yellow Luminescence band (YLB) decreased after the irradiation of a below-gap excitation source of 1.17 eV. The conventional energy schemes and recombination models have been considered to explain our experimental result but only one model in which YLB is the transition of a shallow donor to a deep state placed at ∼1 eV above the valence band maximum satisfies our result. The defect related parameters that give a qualitative insight in the samples have been evaluated by systematically solving the rate equations and fitting the result with the experiment.

Study of Nonradiative Recombination Centers in n-GaN Grown on LT-GaN and AlN Buffer Layer by Below-Gap Excitation

“…AGE power density dependence of the normalized PL intensity (I N ) for samples A and B.increases which results in higher BGE effect due to the enhancement of the non-radiative recombination. Similar AGE density dependence of the I N was observed in our previous studies of TWEPL[22] [25][26] [27].…”

“…The rate equations of the two levels model as shown in Figure 5 can be written below with charge neutrality condition (CNC) [22] ( ) For simplicity, we assumed that the electron capture coefficient C n1 is equal to radiative recombination coefficient B, as 1.2 × 10 −11 cm 3 •s −1 for GaN [32]. Such consideration has been taken by other researchers [26] [33]. Reshchikov et al [1] [34] have reported that the hole capture coefficient of C p1 is in the order of 10 −6 cm 3 •s −1 for GaN.…”

Spectral change of intermediate band luminescence in GaP:N due to below‐gap excitation: Discrimination from thermal activation

“…Combination of experimental intensity change as a function of the BGE density with the rate equation analysis of trap filling effect based on the SRH statistics enabled us to open a way of determining CR parameters quantitatively as the scheme of two‐wavelength excited photoluminescence (TWEPL) . Detection and investigation of CR levels have already been reported for different types of semiconductors like GaAs/AlGaAs QWs , GaN/InGaN QWs , AlGaN QWs , GaN , GaP 1− x N x , and Ba 3 Si 6 O 12 N 2 :Eu 2+ phosphors .…”

Study of optical properties of bulk GaN crystals grown by HVPE

“…Consequently, in the HVPE growth process, the Si impurity will be introduced by the quartz reactor tube and trapped around the dislocations. Moreover, the YL band is believed to be related to the deep states (located at~1 eV above the valence band) [6]; in particular, it is assumed to be the result of a donoreacceptor pair recombination from a shallow donor to a deep acceptor in undoped GaN [19,35]. Based on the above understandings, we consider that in our high-quality FS GaN, the Si donors around the dislocations, which are reasonable sources of shallow donors, will recombine with potential deep acceptors (V Ga ) and finally respond with the YL.…”