Be diffusion in molecular beam epitaxy-grown GaAs structures

Abstract

Beryllium diffusion is considered in heavily doped p-type GaAs structures grown by molecular beam epitaxy (MBE). Secondary ion mass spectrometry (SIMS) measurements performed on samples which underwent rapid thermal processing (RTP) experiments at 850 °C for 30 s show that (i) Be diffusion is faster in p/p+/p structures than in p/p+ ones and (ii) an increase of the As4/Ga flux ratio during the MBE growth affects Be diffusion only in p/p+ structures. These results are discussed by modeling Be diffusion according to a substitutional–interstitial diffusion mechanism where Be transition from substitutional to interstitial takes place by a kick-out process. The modeling procedure, which has been previously used to simulate Be and Zn diffusion in GaAs and in other related compounds, has been modified in order to account for the lacking of equilibrium in the initial concentration of Ga interstitials. It is shown that when the lacking of equilibrium is accounted for at the beginning of the annealing experiment, a satisfactory description of the SIMS results has been achieved in both p/p+ and p/p+/p structures, also considering samples grown by different As4/Ga flux ratios. The modeling results allow us to conclude that in the p/p+/p structures the concentration of point defects (e.g., IGa) in the regions cladding the base layer affects, to a major extent, Be diffusion during RTP, so that an efficient reduction of Be diffusivity is expected only when the whole structure is grown by high V/III flux ratios.

Gallium self-interstitial relaxation in GaAs: Anab initiocharacterization

“…The suggested states varied from neutral 4 , to +1 5,6,7 , +2 8,9,10 , or both +2 and +3 11,12 . Recently, however, Bracht et al 1 found that fits of recent as well as earlier diffusivity profiles are more accurate for dominant neutral and +1 charge states.…”

Photoluminescence properties of Be-doped GaAs/(AlGa)InP heterostructures subjected to annealing processes

“…As it is known, high beryllium doping of heterojunctions results in considerable Be diffusivity all along the differently doped layers [8]. For sample S940, higher Be-diffusion could be expected as compared to S1000 due to the larger doping mismatch between the GaAs and AlGaInP layers (3 Â 10 19 and 1:1 Â 10 18 ; respectively).…”

Diffusion mechanism of implanted Be in GaAs

“…The studies of the formation energy of the Ga self-interstitials in GaAs have shown that their charge state can be +1 [20], +1 or +3 [21], +1 and +2 and +3 [22]. In this way, the singly [5,9,10] and doubly [7,8,11] positively charged Ga interstitial point defects were used in kick-out models of Be diffusion in GaAs. Some authors have employed the neutral Ga selfinterstitials in their corresponding models [4,6].…”

“…From the studies of Be diffusion near the p-n junctions [6] as well as the concentration dependence of Be diffusivity [16,17] and also from the simulations [4,5,[9][10][11], the values of 0 [4,16] and +1 [5,6,[9][10][11]17] have been proposed for Be interstitial charge state.…”