Control of metamorphic buffer structure and device performance of In_xGa_1−xAs epitaxial layers fabricated by metal organic chemical vapor deposition

Abstract

Using a step-graded (SG) buffer structure via metal-organic chemical vapor deposition, we demonstrate a high suitability of In0.5Ga0.5As epitaxial layers on a GaAs substrate for electronic device application. Taking advantage of the technique's precise control, we were able to increase the number of SG layers to achieve a fairly low dislocation density (∼10(6) cm(-2)), while keeping each individual SG layer slightly exceeding the critical thickness (∼80 nm) for strain relaxation. This met the demanded but contradictory requirements, and even offered excellent scalability by lowering the whole buffer structure down to 2.3 μm. This scalability overwhelmingly excels the forefront studies. The effects of the SG misfit strain on the crystal quality and surface morphology of In0.5Ga0.5As epitaxial layers were carefully investigated, and were correlated to threading dislocation (TD) blocking mechanisms. From microstructural analyses, TDs can be blocked effectively through self-annihilation reactions, or hindered randomly by misfit dislocation mechanisms. Growth conditions for avoiding phase separation were also explored and identified. The buffer-improved, high-quality In0.5Ga0.5As epitaxial layers enabled a high-performance, metal-oxide-semiconductor capacitor on a GaAs substrate. The devices displayed remarkable capacitance-voltage responses with small frequency dispersion. A promising interface trap density of 3 × 10(12) eV(-1) cm(-2) in a conductance test was also obtained. These electrical performances are competitive to those using lattice-coherent but pricey InGaAs/InP systems.

Unexpected Aspects of Strain Relaxation and Compensation in InGaAs Metamorphic Structures Grown by MOVPE

“…, and references therein) in the tensile strained region (Figure d), we caution the reader on the limits of the technique in this respect, which here would simply show a modulation in the TEM contrast/color. In our case the phase separation could have been partially suppressed by the high temperature and V/III ratio used during the growth, which are known to have that effect in MOVPE . We also observe that our AFM analysis suggests a very small number of defects (the methodology of ref , based on counting defect related features by AFM, should be taken carefully in its capability of giving absolute, exact values, nevertheless the relative reduction in defect number is likely to be reliable).…”

Effect of Si and Zn doping on surface defects in AlGaInAs compositionally graded buffer by MOCVD

“…2) To avoid dislocation nucleation in mismatch growth, it is critical to maintain a small but constant stress and maximize mismatch dislocations' glide length. 3) Compositionally graded buffers (CGBs) are the most commonly used metamorphic buffers which can produce highly relaxed buffers with smooth surfaces and minimize the threading dislocation density (TDD) through a nucleationlimited mechanism. 4) Many different materials, such as InGaAs, InAlAs, InGaP, GaAsP, GaAsSb, AlGaInAs, AlGaInP, InGaAsP and AlGaAsSb, have been used as metamorphic buffer layers.…”