A versatile digitally-graded buffer structure for metamorphic device applications

Abstract

Exploring more effective buffer schemes for mitigating dislocation deficiencies is the key technology towards higher performance metamorphic devices. Here we demonstrate a versatile metamorphic grading structure consisting of 38-period alternated multilayers of In 0.52 Al 0.48 As and In 0.82 Al 0.18 As on InP substrate, thicknesses of which in each period were gradually varied in opposite directions from 48.7 and 1.3 nm to 1.3 and 48.7 nm, respectively, akin to a digital alloy. Both preferentially dislocation nucleation and blocking of threading dislocation transmission are observed near the In 0.82 Al 0.18 As/In 0.52 Al 0.48 As interfaces, which help relax the strain and lower the residual defect density. A 2.6 μm In 0.83 Ga 0.17 As pin photodetector is fabricated on this pseudo-substrate, attaining a low dark current density of 2.9 × 10 −6 A cm −2 and a high detectivity of 1.8 × 10 10 cmHz 1/2 W −1 at room temperature, comparable with the states of the art that on linearly-graded buffer layers. These results indicate such digitallygraded buffer structures are promising for enhancing performances of metamorphic devices, and can be easily generalized to other lattice-mismatched material systems.

Short-wave infrared InGaAs photodetectors and focal plane arrays

“…Under this practically restrictive condition, the buffer strategy, or using a thinner buffer to reach better effects, are the most important concern. Keeping this in mind, different types of buffer structures have been investigated including linear graded, [47] con-128102-4 vex graded, [48] step graded, [49] composition overshoot, [50] and the combinations, [51] and the inserting of digital alloy into the buffer, [52] while total digital graded buffer structures [53] have also been verified. Optimal growth parameters of the buffer have been investigated in detail.…”

“…Optimal growth parameters of the buffer have been investigated in detail. [42][43][44][45][46][47][48][49][50][51][52][53] Generally speaking, linear graded buffer of accredited thickness is suitable for the devices, and the overall effects are acceptable. Inserting more interfaces into the buffer structure has a positive effect on the buffer quality, especially at the beginning of buffer growth, whereas the total thickness of the buffer is still a pivotal factor.…”