Growth and characterization of orientation patterned GaAs crystals for non-linear optical frequency conversion

Abstract

Orientation patterned (OP)-GaAs crystals have high potential as non linear optical systems. Mid-infrared and terahertz lasers sources can be fabricated with these crystals by frequency conversion from shorter wavelength sources. The optical propagation losses are critical; therefore, the OP-GaAs crystals must have high quality with low incorporation of defects and high homogeneity to reduce the refractive index fluctuations. Defects with electro-optic signature must be characterized in order to reduce their presence. Cathodoluminescence studies of these crystals permit the distribution of the main defects to be established, both extended and point defects. Special attention is paid to the role of the walls between the two domain orientations, and to the incorporation of impurities in Si-doped samples.

Cathodoluminescence characterization of Si-doped orientation patterned GaAs crystals

“…The band peaking at 1000 nm, associated with Si Ga -V Ga complexes (15), follows a similar distribution to the V Ga related band peaking at 910 nm (1.36 eV) in undoped OP-GaAs crystals (9), in particular, it shows similar enhancement at the domain wall, which is consistent with the presence of the V Ga defects in the complex responsible for this emission. The distribution of the 1200 nm band around the domain wall is different, it is not symmetric at both sides of the wall, because it is related to the Si As -Si Ga complex (16), which the distribution is probably governed by Si As ; one expects a higher concentration of Si As in the [00-1] domain because of the lower [As] in that domain orientation.…”

“…This is particularly clear around the domain wall, where one observes an increase of the emission in the [00-1] domain and a decrease in the [001] domain. The higher concentration of Si As defects in the [00-1] domains is also consistent with the distribution of the max and FWHM parameters of the NBE emission, because the presence of Si As produces self compensation, with the concomitant reduction of the free electron concentration in the [00-1] domains, as deduced from the redshift of the NBE peak in the [00-1] domain with respect to the [001] domain; note that the peak and FWHM distributions over the Si-doped OP-GaAs crystal are different from those observed in undoped OP-GaAs crystals, in which the the peak and FWHM distributions mainly accounted for the residual stress induced by the domain wall (9).…”

“…The use of a low pressure reactor, instead of an atmospheric reactor, allows a more efficient use of the reactant gases at high velocity and high partial pressure. The system consists of a horizontal quartz tube, heated by a three-zone furnace (allowing the control of the GaCl source temperature, mixing temperature and substrate temperature, repectively (9,10), and sealed to allow low pressure operation in the range of 1 to 5 torr. The arsenic source consists of arsine (AsH 3 ), which decomposes on the sample surface; while, the Si doping source was the chlorosilane formed in situ by the reaction between HCl and Si arising from the reactor walls.…”