Detailed atomic scale structure of AlInAs/GaInAs quantum wells

Abstract

Quantification of high-resolution transmission electron microscopy (HRTEM) lattice images and detailed luminescence line-shape analysis is used to determine the atomic structure of GaInAs quantum wells (QWs) between AlInAs barriers. By careful analysis of a statistically large number of HRTEM images, we are able to measure the standard deviation in the mean quantum-well width to better than one (200) monolayer. Statistical analysis of the temperature dependence of the luminescence yields QW width distribution functions and variations of the mean QW width across the sample with a precision of better than 0.2 nm in quantitative agreement with the transmission electron microscopy results. No large and smooth islands with monolayer steps in between but rather long-range mean band-gap fluctuations are observed. Spectral broadening is found to be induced by well-width-dependent roughness of inequivalent growth surfaces and by clustering in the barriers for extremely narrow wells of the order Lz≊1 nm. Our results indicate a pronounced surface roughening of InGaAs at 640 °C. The mean height of steps of a maximum width of 5 nm at the InGaAs surface increases from 1 to 2 monolayers for an increase of well width from ≊1 to 2.5 nm.

Proposed graphene nanospaser

“…However, the graphene patch is so small (,10 nm in our case) that it is likely to completely lie within one homogeneous domain of the quantum well walls, which is approximately 10-30 nm. [40][41][42] Consequently, the polarization relaxation rate is expected to be C 12 5h 2 /t 12 , where t 12 is the lifetime for the intersubband transition 2w? 1w j j , whose typical value for the quantum well cascade systems is 43,44 t 12 5h 2 /C 12 <1 ps, corresponding to C 12 <0.66 meV.…”

Scanning cathodoluminescence microscopy: A unique approach to atomic-scale characterization of heterointerfaces and imaging of semiconductor inhomogeneities

“…[11][12][13][14][15] In any of these cases a quantitative characterization requires a spatial resolution <p,m. Transmission electron microscopy (TEM) [16][17][18][19] and especially high-resolution TEM (HRTEM) and chemical imaging provide subatomic resolution together with chemical sensitivity. 16,18 However, a most skillful, time consuming, and destructive sample preparation is essential for all TEM techniques.…”