Mechanical stress in InP and GaAs ridges formed by reactive ion etching

Abstract

The mechanical deformation induced by reactive ion etching (RIE) of rectangular ridge waveguides in GaAs and InP has been investigated by photoluminescence and cathodoluminescence techniques. Several trends were identified and are discussed.First, it is concluded that the RIE process itself is the source of the mechanical deformation. A compressive volume change occurs mainly within the ridge (with a maximum close to the vertical etched sidewalls), extending outside the ridges, up to several µm below the bottom etched surface. An anisotropic deformation also appears, again mainly close to the etched sidewalls and below the bottom etched surface. A narrow area under tensile stress was also identified, localized outside the ridges and in a shallow region below the bottom etched surface. Cumulative, overlapping effects are seen, inside the ridges where the compressive stress fields originating at the vertical etched sidewalls contribute to an overall compression inside the ridge which increases as the ridge width decreases. In addition, a tensile stress is also observed outside the ridge, strongly enhanced by the presence of neighbouring ridges. These conclusions are significant for the design of photonic structures. Because of the photoelastic effect, which is important in GaAs and InP, the properties of devices such as waveguides might be affected by the mechanical stress described herein.

Low temperature micro-photoluminescence spectroscopy of microstructures with InAsP/InP strained quantum wells

“…The origin of this mechanical stress could be related to the ion bombardment taking place during exposure to the etching plasma. As previously described in [5], the resulting crystal deformation consists mainly of a hydrostatic volume compression taking place at the vertical etched sidewalls and extending several microns inside the stripes. Such volume compression should change the band gap, which was actually observed by both µPL and spatially resolved cathodoluminescence.…”

“…Therefore, we suggest that the reduction of the PL intensities is caused predominantly by a local modification of the electronic band structure within the QWs, resulting from a crystal deformation due to mechanical stress introduced by the etching process. The occurrence of mechanical stress during RIE of stripes in GaAs and InP has been demonstrated recently by Landesman et al [5]. The origin of this mechanical stress could be related to the ion bombardment taking place during exposure to the etching plasma.…”

“…In particular, the local PL intensity is affected by the mechanical stress within the stripes. First, as was demonstrated recently, the RIE process itself can introduce some mechanical stress, probably due to diffusion and implantation of ions / reactive radicals near the etched sidewalls [5]. Secondly, as the InAs x P 1−x QWs were grown with compressive built-in stress, stress relaxation occurs near the etched sidewalls which are free surfaces.…”

Domain wall magnetic tunnel junction-based artificial synapses and neurons for all-spin neuromorphic hardware

“…According to the relationship of i DMI and t W unveiled in Fig. 1f , the dedicatedly etched regions hold a larger i DMI with thinner W thickness due to the ion milling introduced local compression stress at the W/CoFeB interface 60 , 61 , which reduces distance between 5 d and 3 d atoms at the interface leading to an enhanced 3 d −5 d orbital hybridization 62 – 64 . It is noteworthy that the DW energy density (σ DW ) is closely related to i DMI strength 65 , …”