Epitaxial liftoff of ZnSe-based heterostructures using a II-VI release layer

Abstract

Epitaxial liftoff is a post-growth process by which the active part of a semiconductor heterostructure, the epitaxial layer, is removed from its original substrate and deposited onto a new substrate. This is a well established technique in GaAs-based heterostructures where epitaxial liftoff can be achieved by exploiting the contrast in the etch rates of GaAs and AlAs in hydrofluoric acid. We report here successful epitaxial liftoff of a ZnSe-based heterostructure. We find that a metastable layer of MgS acts as a perfect release layer based on the huge contrast in the etch rates of ZnSe and MgS in hydrochloric acid. Epitaxial liftoff of millimeter-sized ZnSe samples takes a fraction of the time required for GaAs liftoff. Photoluminescence experiments confirm that the liftoff layer has the same optical characteristics as the original wafer material.

Metastable II–VI sulphides: Growth, characterization and stability

“…For most applications, MgS has been replaced in barriers by Zn 0.2 Mg 0.8 S 0.64 Se 0.36 , and is instead used as a sacrificial etching layer [27]. II-VI epitaxial layers deposited on an MgS layer 5-10 nm thick can be easily detached from the substrate with little change in the strain and PL efficiency of the layers and we have shown that structures containing both an MgS release layer and Zn 0.2 Mg 0.8 S 0.64 Se 0.36 , barrier layers can be fabricated [28].…”

Determination of the etching mechanism in MgS and ZnMgSSe epitaxial lift‐off layers

“…Our usual wax deposition method is to melt small pieces directly on the epilayer surface [1][2][3], while for AlAs a solution of wax in trichloroethylene was used [6]. Although we have not compared all t, so far we have found no real difference in the etching speed between the two methods.…”

“…1 Introduction Recently, we developed a technique for epitaxial lift-off of a II-VI semiconductor structure from a GaAs substrate by introducing a sacrificial layer of MgS underneath the epilayer [1]. This technique allows the transfer of the active epilayer to a new substrate giving extra functionality, for example by removing (Zn,Cd)Se structures from GaAs to make microcavities [2,3].…”

“…2 Etching of MgS sacrificial layers 2.1 Experimental method Four epitaxial layers were grown by MBE on GaAs (100) substrates with the structure ZnSe(20 nm)/MgS(t)/ZnSe(53 nm)/ 4 Â (Zn 0.9 Cd 0.1 Se(8 nm) þ ZnSe(8 nm))/ZnSe(67 nm) using the procedure described previously [1,7]. The MgS layer thicknesses were t ¼ 2, 3, 20, 30 nm.…”

“…After growth, the samples were cleaved into 3 mm  3 mm squares and then the epilayer was coated with apiezon wax. The samples were etched as previously [1][2][3] in 10% HCl and the etching speed was calculated from the time required to remove the entire MgS layer. All the samples etched easily, apart from the sample with t ¼ 2 nm, which did not etch at all.…”