Moving photoluminescence band in AlGaN/GaN heterostructures

Abstract

AlGaN/GaN heterostructures with two-dimensional electron gas (2DEG) grown by metal organic chemical vapor deposition were investigated by photoluminescence (PL) spectroscopy. The PL spectra of these heterostructures contain an unusual band assigned to quasi-donoracceptor recombination transitions (Q-DAP) from small-size regions of the GaN layer with perturbed conduction and valence band edges. The Q-DAP band dominates the delayed nonstationary PL spectra; its energy position changes strongly with time after the excitation pulse (up to 160 meV within 10 μs). The Q-DAP band intensity decreases under continuous excitation during tens of minutes. The appearance of the Q-DAP band is accompanied by a rise in the intensity of the PL bands associated with 2DEG.

Low-Temperature and Ammonia-Free Epitaxy of the GaN/AlGaN/GaN Heterostructure

“…In addition, the 2DEG features (ground and excited states) are reported in a quite wide energy range from 3.44 and 3.47 eV. 30,31,33 Despite their spectral position, the behavior of the x 1 and x 2 bands, as a function of excitation power, excludes the involvement of the 2DEG states in the recombination process, since there is no blue-shift evidence with increasing excitation power (which could be from a few to hundreds of meV). 31 In addition, the x 2 band can be traced up to ∼180 K, well beyond the typical temperature range reported in the literature (40− 100 K).…”

“…At high temperatures, x 1 and x 4 are no longer visible while x 2 and x 3 show the characteristic energy red shift with temperature. 32 The typical experimental energy values reported in the literature for GaN excitonic complexes in "strained" AlGaN/ GaN heterostructures at low temperature 30,31,33 are as follows: ∼3.47 eV (A 0 X neutral acceptor bound), ∼3.48 eV (D 0 X neutral donor bound), ∼3.49 eV (FE n=1 free-exciton ground state), and ∼3.51 eV (FE n=2 free-exciton excited state). In addition, the 2DEG features (ground and excited states) are reported in a quite wide energy range from 3.44 and 3.47 eV.…”

“…AlGaN/GaN heterostructures at low temperature, 28,29,31 are the following: 3.47 eV (A 0 X neutral acceptor bound), 3.48 eV (D 0 X neutral donor bound), 3.49 eV (FEn=1 free-exciton ground state), 3.51 eV (FEn=2 freeexciton excited state). Additionally, the 2DEG features (ground and excited states) are reported in a quite spread energy range from 3.44 eV and 3.47 eV.…”

Thermometry of AlGaN/GaN 2D Channels at High Electric Fields Using Electrical and Optical Methods

“…To prevent laser heating, the µ‐RS measurements were performed under 488 nm (2.54 eV) excitation of the Ar–Kr laser. [ 26–30 ] In these conditions, the vertical absorption depth in the GaN is ≈80 nm. [ 17 ] The spectrometer HORIBA Jobin‐Yvon T64000 equipped with a confocal microscope and Peltier cooled ANDOR CCD camera was used for spectra registration and laser beam focusing.…”

“…At room temperature, µ-PL spectrum of the GaN-based structure dominates with a single donor-bound exciton (D 0 X) emission band at 3.42 eV. [27][28][29][30][31] Applying the electric field leads to the peak red shift of the D 0 X band within the range 3.42-3.40 eV at electric fields up to 1.65 kV cm −1 . The mentioned shift is caused by the temperature increase due to Joule self-heating and the mechanical strain increase in the AlGaN/GaN heterostructure.…”