Diffusion in isotopically controlled semiconductor systems

Quantitative compositional profiles of enhanced intermixing in GaAs/AlGaAs quantum well heterostructures annealed with and without a SiO2cap layer

“…The inter-diffusion coefficients were directly obtained from the width of the concentration profiles by using the Boltzmann-Matano analysis in the form 2 , where L D is the diffusion length, t is annealing time, D i is the interdiffusion coefficient and x i is the full width half maximum (FWHM) of the as-grown QW, while x f is the FWHM after anneal for time, t. Figures 2(a In comparison, reported activation energies for Ga-Al interdiffusion range from 1 eV to 6.2 eV, and values of the pre-factor range over 22 orders of magnitude, as shown in [13]. Our value of the activation energy obtained for uncapped structures is close to those previously reported in [13][14][15], while the activation energy for SiO 2 capped samples is lower compared to some previously reported [16,17] (2.72 eV).…”

“…In comparison, reported activation energies for Ga-Al interdiffusion range from 1 eV to 6.2 eV, and values of the pre-factor range over 22 orders of magnitude, as shown in[13]. Our value of the activation energy obtained for uncapped structures is close to those previously reported in[13][14][15], while the activation energy for SiO 2 capped samples is lower compared to some previously reported[16,17] (2.72 eV).Ga diffusion into SiO 2 has been observed[18,19] and it is generally accepted[2,10] that larger QWI for SiO 2 capped samples occurs due to this Ga out-diffusion leaving behind a high concentration of vacancies in the top GaAs layer, which enhances the inter-diffusion. However, vacancy diffusion is not expected to result in the square-like evolution of the QWs[11].…”

Molecular Dynamics Analysis of Diffusion of Point Defects in GaAs

“…[1][2][3] Since the total number of dislocations at which such point defects are absorbed has been reduced due to the development of growth techniques such as the vapor pressure-controlled liquid-encapsulated Czochralski ͑CZ͒ method ͑VLEC͒ and the vertical gradient freezing method ͑VGF͒, the effects of such point defects on the electronic characteristics of substrates has become dominant.…”

“…Control of the distribution of point defects in growing crystals of GaAs is a key issue for fabrication of a high-quality power amplifier in a cellular phone, because such control enables the stabilization of deviation of the Fermi level due to the unbalance of charge compensation in semi-insulating gallium arsenide ͑GaAs͒ substrates. [1][2][3] Since the total number of dislocations at which such point defects are absorbed has been reduced due to the development of growth techniques such as the vapor pressure-controlled liquid-encapsulated Czochralski ͑CZ͒ method ͑VLEC͒ and the vertical gradient freezing method ͑VGF͒, the effects of such point defects on the electronic characteristics of substrates has become dominant.…”