Quantitative and Depth-Resolved Investigation of Deep-Level Defects in InGaN/GaN Heterostructures

Abstract

0.17 Ga 0.83 N/In 0.02 Ga 0.98 N/p-GaN:Mg heterostructures were studied using deep-level optical spectroscopy (DLOS). Depth-resolved DLOS was achieved by exploiting the polarization-induced electric fields to discriminate among defects located in the In 0.17 Ga 0.83 N and the In 0.02 Ga 0.98 N regions. Growth conditions for the In x Ga 1Àx N layers were nominally the same as those in InGaN/GaN multi-quantum-well (MQW) structures, so the defect states reported here are expected to be active in MQW regions. Thus, this work provides important insight into defects that are likely to influence MQW radiative efficiency. In 0.17 Ga 0.83 N-related bandgap states were observed at E v + 1.60 eV and E v + 2.59 eV, where E v is the valence-band maximum, compared with levels at E v + 1.85 eV, E v + 2.51 eV, and E v + 3.30 eV in the In 0.02 Ga 0.98 N region. A lighted capacitance-voltage technique was used to determine the areal density of deep states. The possible origins of the associated defects are considered along with their potential roles in light-emitting diodes.

Effects of quantum well growth temperature on the recombination efficiency of InGaN/GaN multiple quantum wells that emit in the green and blue spectral regions

“…13 There is also a growing body of evidence that point defects are introduced into InGaN layers as the indium composition is increased. [14][15][16][17] For example, recent theoretical calculations have shown that nitrogen vacancies have the lowest formation energy in InN 18 or InGaN alloys with high indium compositions. 19 It has also been demonstrated that point defects act as non-radiative recombination centers, leading to a reduction in the non-radiative recombination lifetime.…”

Detailed characterization of deep level defects in InGaN Schottky diodes by optical and thermal deep level spectroscopies

“…Indeed, Armstrong et al observed a level found by DLOS at Evþ1.60 eV in In 0.17 Ga 0.83 N/p-GaN heterojunctions that were grown using similar conditions to quantum-well LEDs. 20 In summary, we have demonstrated high quality Au/Ag/ In 0.2 Ga 0.8 N Schottky diodes and have subsequently used them to explore deep levels throughout In 0.2 Ga 0.8 N bandgap by using both thermal and optically based trap spectroscopic methods. Five deep states were detected throughout the bandgap of In 0.2 Ga 0.8 N with energy levels at Ec-0.39 eV (DLTS), Ec-0.89 eV (DLTS), Ec-1.45 eV (DLOS), Ec-1.76 eV (DLOS), and Ec-2.50 eV (DLOS).…”

Investigating defects in InGaN based optoelectronics: from material and device perspective

“…In equation (16), equilibrium carrier density in the QW is n 0 and ideality factor is denoted as , h V T is the thermal voltage. In equation (17), r V ( )is the fraction of carriers that recombine. Filling factor of defects is defined as f…”

“…Low growth temperatures lead to inadequate sidewall diffusion and poor crystal quality of InGaN nanowires with high indium incorporation. Studies have shown that point defects surge significantly with high indium composition [17,18]. Nitrogen vacancies have the lowest formation energy in InN or InGaN with high indium composition [19,20].…”