Evidence for Shallow Acceptor Levels in MBE Grown GaN

Abstract

We report the results of photoluminescence measurements on a number of GaN thin films grown by MBE on GaAs (111)B substrates. In particular, we draw attention to a new observation of a line at approximately 3.40eV which is accompanied by complex fine structure and interpret it as due to a donor-acceptor (DA) transition. Assuming a donor energy of 30meV, we derive an acceptor binding energy of approximately 80meV which is very much smaller than the accepted value of 250meV for the well established Mg acceptor. However, our result is in agreement with a recent estimate of the hydrogenic acceptor energy as being 85meV.

Energy bands and acceptor binding energies of GaN

“…The PL is similar to the results of Ref. 5. The multipeak structure for the 3.38-3.40 PL peak is assigned to the transitions from donor state to ⌫ 6 S and ⌫ 1 S acceptor states.…”

“…Based on this, the effectivemass acceptor ionization energy in GaN is estimated to be 85Ϯ8 meV. In a recent optical experiment 5 Ren et al observed a new line at approximately 3.40 eV, which is accompanied by complex fine structure, and interpreted it as due to a DA transition. Assuming a donor binding energy of 30 meV, they derived an acceptor binding energy of approximately 80 meV.…”

Photoluminescence study of Si-doped (112̄0)a-plane GaN grown on (11̄02)r-plane sapphire by metalorganic chemical vapor deposition

“…We intend to interpret the experimental results to the crystal orientation of ð1 1 % 2 0Þ GaN. A series of experiment results assign the emission around 3.40 eV to DAP [22] or bound exciton transition [14]. The temperature dependent PL spectra of samples A and B were measured to study the intense emission.…”

“…Due to the PL results and the FWHM of this peak, this line can be attributed to DAP transition. Using the method presented by Ren et al [22], we calculate the binding energy of acceptor related to the DAP transition as approximately 80 meV. According to some experimental results [9,23], there exist highdensity planar defects that mostly originate on the c-plane sidewalls of three-dimension islands in ð1 1 % 2 0Þ GaN.…”

Metalorganic Vapor Phase Epitaxy Growth of m-Plane GaN Using LiAlO2 Substrates

“…This result could be attributed to the donor-bound exciton (D 0 X) transition. 8,16) In addition, the D 0 X transition (about 3.52 eV) of the m-plane GaN blueshifted in comparison with that of the relaxed GaN (about 3.47 eV) possibly due to the higher compressive in-plane strain. 17,18) For the B line, the transition (about 3.35 eV) showed a redshift with increasing temperatures, similar to the transition of the structural defect, such as stacking faults.…”