Thick Hydride Vapor Phase Heteroepitaxy: A Novel Approach to Growth of Nonlinear Optical Materials

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.

Thick Heteroepitaxy of Binary and Ternary Semiconductor Materials for Nonlinear Frequency Conversion in the Mid and Longwave Infrared Region

“…Optimization of the reactor configuration and process parameters resulted in a significant increase of the growth rate [ 22–24 ] and improvement of the surface morphology and crystalline layer quality compared to our previously reported efforts. [ 20,33,34 ] Faster growth rates of up to 210 μm h −1 for growths with 1 h duration (Table 2: run 1), smoother surface morphology (RMS = 1–2 nm), and crystalline quality similar to the commercial substrate quality were achieved with GaP/GaAs, GaAs/GaP, GaAs x P 1‐ x /GaAs, and GaAs x P 1‐ x /GaP heteroepitaxy.…”

“…Note also that these pits appear on both patterned and unpatterned surfaces on binary and ternary materials, which means they are not correlated to the pattern deposition or to the chemical composition. Although some authors associate the appearance of these pits with the polarity of the inverted layer, we are more inclined to believe that in the case of heteroepitaxy, including GaAs x P 1‐ x ternaries, the pits’ appearance is due to rather the initial exposure of the substrate or template surface to the non‐native precursor, PH 3 , AsH 3 , or their mixture [ 24,25 ] .…”

“…During this exposure, the non‐native precursor not only etches the surface of the oppositely oriented domain differently (leaving longitudinal pits in mutually perpendicular directions [ 24 ] ) but also predetermines the follow‐on HVPE growth. Obviously, at certain conditions the HVPE growth is more favorable to one of the domain orientations—the one in which domains propagate along [01ī] direction and are associated with the growth on the substrate surface, than the one in which domains propagate along the opposite [011] direction and are associated with the growth on the inverted layer.…”

“…The idea to grow GaAs x P 1‐ x ternaries, discussed in more detail in this work, came from our belief that the growth of a ternary should be a more favorable heteroepitaxial case than the growth of one binary material on another, and the possibility to obtain a material with lower 2PA than GaAs but with higher nonlinear susceptibility than GaP. Both ideas, heteroepitaxy and ternaries, are now being explored by several groups in the United States [ 22–24 ] and Europe [ 25,26 ] to obtain large enough optical apertures by thick growth on OP templates. Before proving frequency conversion in heteroepitaxially grown materials, including ternaries, however, one should bear in mind that the birefringence stress due to lattice and thermal mismatch during heteroepitaxy or the refractive index inhomogeneity could be new problems to think of.…”

Direct Heteroepitaxy of Orientation‐Patterned GaP on GaAs by Hydride Vapor Phase Epitaxy for Quasi‐Phase‐Matching Applications

“…However, OP‐GaP growth on OP‐GaAs templates prepared by a wafer fusion approach has not been as successful, with (00) domains being “pinched off” after around 75 μm of growth . Therefore, it is desirable to address the growth on wafer‐bonded templates to reap the benefits of OP‐GaAs templates fabricated by wafer fusion …”