Impurity induced layer disordering of Si implanted AlxGa1−xAs-GaAs quantum-well heterostructures: Layer disordering via diffusion from extrinsic dislocation loops

Abstract

Extensive data are presented on impurity-induced layer disordering (IILD) of AlxGa1−xAs-GaAs quantum-well heterostructures and superlattices that are Si implanted and annealed (Si+-IILD) at three different implant doses. We show that impurity activation is not critical to the layer disordering process and that Si diffusion from the implanted profile initiates Si+-IILD. When the implant dose is as high as φ≥5×1013/cm2 (nSi ≥2×1018/cm3), Si interstitial loops (Si-ILs) form by diffusion and agglomeration of the implanted Si atoms during the initial stages of annealing. If a source of Ga vacancies is provided (e.g., via an As overpressure or SiO2 encapsulation), the Si-ILs dissociate and supply Si atoms for diffusion and hence Si+-IILD during the latter stages of annealing. If a Si3N4 encapsulant is employed, however, fewer Si-ILs form and Si diffusion is inhibited. For an implantation dose as low as φ=1×1012/cm2 (nSi =3×1016/cm3), extensive Si+-IILD is realized via capless annealing and Si-ILs are not observed. It is significant for device applications that the layer-disordered material operates as a cw 77 K photopumped laser, which indicates that the layer averaging (IILD) does not damage the crystal.

Disordering of Quantum Structures for Optoelectronic Device Integration

“…IFVD does not introduce significant damage/ impurities, thereby high crystal quality and low optical propagation losses can be maintained in the sample. Other dielectric films, such as Si 3 N 4 (Guido et al, 1987), SrF 2 (Beauvais et al, 1992), P-doped SiO 2 and Ga-doped spin-or glass (Fu et al, 2002a) have been used to suppress intermixing, among which the most notable are SrF 2 and Si 3 N 4 . However, the mechanism of IFVD can be quite complicated, although it only contains two steps that occur almost simultaneously: (1) the generation of point defects and (2) the diffusion of point defects.…”

Suppression of quantum well intermixing in GaAs/AlGaAs laser structures using phosphorus-doped SiO2 encapsulant layer

“…A number of masking dielectric materials or techniques have been reported, most notably using SrF 2 , 3 Si 3 N 4 , 4 and a hydrogen passivation technique. 5 SrF 2 is an effective mask for QW intermixing suppression and has been used in conjunction with SiO 2 caps to fabricate photonic integrated devices such as extended cavity lasers 6 and integrated passive waveguides for distributed Bragg reflectors.…”

“…9 A hydrogen passivation technique has recently been demonstrated as an effective mask for QW intermixing suppression in undoped structures. 4 The main limitation of this technique is that it is only effective at relatively low temperatures ͑900°C͒, and the possibility of transferring this technique to the more common doped p-i-n laser structures used in optoelectronics is still under investigation.…”

Investigations of impurity-free vacancy disordering in (Al)InGaAs(P)/InGaAs quantum wells

“…The most commonly used encapsulation layer to promote intermixing in GaAs-based systems is SiO 2 and it is well known that IFVD is promoted by outdiffusion of Ga into the SiO 2 and diffusion of the resultant Ga vacancies across the heterointerfaces. Other dielectric films such as Si 3 N 4 [12], SrF 2 [13], P-doped SiO 2 [14] and Ga-doped spin-on glass [15] have been used to suppress intermixing, among which the most notable are SrF 2 and Si 3 N 4 . For InP-based materials which are considered as important candidates for their application in 1.55 μm fiber-optic communication systems, although SiO 2 is still found to be able to introduce large bandgap shifts in various QW systems [6,16,17] and Si x N y to suppress intermixing [18], the mechanism for enhanced intermixing by IFVD approaches remains unclear since compositional differences typically exist in both group III and group V sublattices.…”