Cathodoluminescence Study of Orientation-Patterned GaAs Crystals for Nonlinear Optics

Abstract

Orientation-patterned (OP) GaAs crystals are very promising for their use in nonlinear optical applications. In particular, mid-infrared and terahertz lasers can be generated by frequency conversion from shorter-wavelength sources. However, the quality of the crystals is crucial for high conversion efficiency, as the presence of defects with electrooptical signatures can contribute to optical losses. The study of these defects is a step toward the improvement of OP-GaAs crystals. We present here a spectroscopic cathodoluminescence study of the distribution of the main defects. Tentative relations between defects and the optical propagation losses are discussed.

Direct atomic imaging of antiphase boundaries and orthotwins in orientation-patterned GaAs

“…Previous studies of OP-GaAs structures using cathodoluminescence (CL) indicated regions of reduced emission inside the domains located close to APBs. 3,8 We expect that some structural defects might be formed in this material. In order to provide detailed information, conventional transmission electron microscopy (CTEM) and aberration-corrected scanning transmission electron microscopy (STEM) were used for material characterization.…”

“…More details on the fabrication process are given in Ref. 8. Alternatively some samples were also realized by GaAs on GaAs wafer bonding to reverse the GaAs orientation and by atmospheric pressure HVPE for the regrowth step.…”

“…The presence of these defects can influence the optical properties of this material and explain previous observations of cathodoluminescence signal attenuation. 8 Formation of these planar defects will reduce the optical conversion efficiency in mid-infrared and terahertz lasers and other devices based on OP-GaAs structures.…”

Planar defects in patterned GaAs by aberration corrected STEM

“…On average, the last atomic column at the upper side of the boundary is As and the lower side is Ga (shown as inset), showing that the boundary is stoichiometric, despite that the microtwin having reverse growth polarity compared to the matrix. This arrangement could contribute to understand the electro-optical behavior of the inversion domain boundaries in OP crystals [1].…”

“…In the case of oriented patterned Gallium Arsenide (OP-GaAs), which are periodic gratings of inversion domains separated by anti-phase boundaries (APBs), the quality of the crystals is crucial for high conversion efficiency in the mid-infrared and terahertz laser sources. Defects with electro optical signatures contribute to optical losses and therefore understanding them is a step toward to the improvement of the OP-GaAs crystals; in particular, the domain boundaries seem to play a major role in the efficiency conversion [1]. Therefore, a better understanding of their structure will be a step forward to reduce the optical losses.…”