Towards a better understanding of the operative mechanisms underlying impurity-free disordering of GaAs: Effect of stress

Abstract

Arsenic antisite defects in p -GaAs grown by metal-organic chemical-vapor deposition and the EL2 defectThe effect of stress on defect creation and diffusion during impurity-free disordering of SiO x -capped n-GaAs epitaxial layers has been investigated using deep level transient spectroscopy. The oxygen content in the SiO x layer and the nature of the stress that it imposes on the GaAs layer were varied by changing the nitrous oxide flow rate, N, during plasma-enhanced chemical vapor deposition of the capping layer. The peak intensity of defects S1 and S4 increased with the increasing nitrous oxide flow rate to exhibit a maximum in the range 80 sccmϽNϽ200 sccm. Any further increase in N resulted in a decrease in peak defect intensity, which reached an almost constant value for N Ͼ350 sccm. On the other hand, the peak intensity of S2* increased linearly with N. We have explained the maximum in the intensity of defects S1 and S4 for 80 sccmϽNϽ200 sccm to be due to a corresponding maximum in the compressive stress which is experienced by the capped GaAs layer during annealing. Although the creation of S2*, which we have proposed to be a complex involving the gallium vacancy (V Ga ), is enhanced with the increasing compressive stress, it also becomes efficiently converted into the arsenic-antisite, As Ga . The compound effect of these opposing mechanisms results in a linear dependence of the peak intensity of S2* on N. This study is to the best of our knowledge the first to provide the evidence for the stress-dependent anti-correlation between V Ga -and As Ga -related defects in GaAs. We have also narrowed the origin of S1 to complexes involving arsenic interstitials, As i , and/or As Ga .

Intermixing of InGaAs/GaAs quantum wells and quantum dots using sputter-deposited silicon oxynitride capping layers

“…Performing these measurements on epitaxially-grown GaAs samples would avoid the complications that arise from the interfaces in QW or QD structures. 12 In addition to genuine IFVD, sputter-deposited capping layers have also been linked to a form of intermixing that is universal among several III-V materials systems. This study also considered the potential for these depositions to create point defects in the GaAs surface and therefore initiate this intermixing mechanism.…”

“…As Ga , was shown to be more efficient under compressive stress. 12 On the other hand, it is also known that compressive stress in the semiconductor structure will enhance the mobility of vacancies and can pilot them towards the vicinity of buried quantum structures. 11 Therefore, the actual concentration of V Ga in silica-capped QW or QD structures is the result of competition between the V Ga concentration injected at the III-V surface (plus any as-grown vacancies) that are freely mobile within the lattice, and the concentration of V Ga that are consumed in the creation of As Ga defects.…”

“…11 Therefore, the actual concentration of V Ga in silica-capped QW or QD structures is the result of competition between the V Ga concentration injected at the III-V surface (plus any as-grown vacancies) that are freely mobile within the lattice, and the concentration of V Ga that are consumed in the creation of As Ga defects. 12 Presumably, a modest amount of compressive stress in the semiconductor is optimal for IFVD as it will allow V Ga movement towards the QWs or QDs (which are usually on the order of 100 nm below the III-V surface), but it will not excessively drive the creation of As Ga .…”

“…That is, Ga vacancies combine with As interstitials (As i ) to form antisite defects (As Ga ). 12 By consuming V Ga , the degree of intermixing may be reduced, 13 so the relationship between stress and the IFVD mechanism is not straight-forward.…”

Impurity-free quantum well intermixing for large optical cavity high-power laser diode structures

“…Controlled addition of P 2 O 5 into SiO 2 has been used to control the extent of strain and its influence on the quantum well emission has been documented [15]. The role of stress in the inter-diffusion of Ga has been elucidated upon by several groups [16,17]. Patterned Si 3 N 4 layers covered with SiO 2 and patterned SiO 2 layers covered with Si 3 N 4 have been shown to have opposing effects on the intermixing leading to the idea of directed diffusion of point defects such as Ga vacancies.…”