Abstract
At the time when many nonlinear optical (NLO) materials for frequency conversion of laser sources in the mid and long-wave infrared have achieved their fundamental or technological limits, we propose heteroepitaxy as a solution to develop novel NLO materials. Heteroepitaxy, is the most applied method to combine two different materials—by growing one material on another. In this work we show that combining two binary materials in a ternary may significantly improve the NLO properties that are of great importance for the pursued applications. Plus, due to the closer lattice match to the related substrate, a ternary is always a more favorable heteroepitaxial case than the two completely different materials. We also discuss combining different growth methods—one close-to-equilibrium (e.g., hydride vapor phase epitaxy—HVPE) with one far-from-equilibrium (e.g., metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE)) growth processes—to explore new opportunities for the growth of novel heterostructures, including ternary layers with gradual change in composition. The combination of different materials by nature—organics with inorganics—in a hybrid quasi-phase matching (QPM) structure is another topic we briefly discuss, along with some innovative techniques for the fabrication of orientation-patterned (OP) templates, including such that are based on the most universal semiconductor material—Si. Still, the focus in this work is on a series of NLO materials—GaAs, GaP, ZnSe, GaSe, ZnTe, GaN… and some of their ternaries grown with high surface and crystalline quality on non-native substrates and on non-native OP templates using hydride vapor phase epitaxy (HVPE). The grown thick device quality QPM structures were used for further development of high power, compact, broadly tunable frequency conversion laser sources for the mid and longwave infrared with various applications in defense, security, industry, medicine and science.
Highlights
Despite the huge number of commercially available direct laser sources [1] some wavelength regions still remain barely populated
The focus in this work is on a series of nonlinear optical (NLO) materials—GaAs, GaP, ZnSe, gallium selenide (GaSe), ZnTe, GaN . . . and some of their ternaries grown with high surface and crystalline quality on non-native substrates and on non-native OP templates using hydride vapor phase epitaxy (HVPE)
The growth on a patterned substrate or on a buffer layer, especially in the case of heteroepitaxy has a number of advantages: First of all, a pattern of evenly distributed nucleation nano-spots on the foreign substrate surface will promote a more uniform nucleation but will efficiently contribute to the relief of the elastic strain built in result of the lattice and thermal mismatch between substrate and growing layer and in addition to facilitate the separation of the film from the substrate, if necessary
Summary
Despite the huge number of commercially available direct laser sources [1] some wavelength regions still remain barely populated. The fact is that neither OP-GaAs nor OP-GaP could achieve the desired efficiency for frequency conversion devices, that neither one is good enough on its own Combining these two materials by growing heteroepitaxially GaP on the readily available high quality OP-GaAs templates seemed logical. Searching for a solution, we present in this article some of our more efficient and less expensive approaches for OP-GaP and OP-GaAs template preparation, including on the most universal semiconductor material—Si [28] The latter approach is based on the successful combination of two growth processes—one close-to-equilibrium with one far-from-equilibrium. A small section in this article is reserved for a special case heteroepitaxy—Van-der-Waals heteroepitaxy [30] of low-dimensional semiconductor materials such as GaSe
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