Photoassisted Selective Area Growth of III–V Compounds

Abstract

Selective area epitaxial growth of gallium arsenide (GaAs) by laser assisted chemical vapor deposition (LCVD) offers a promising approach to in-situ device fabrication and integration. By scanning a focussed argon ion laser beam across a thermally biased substrate in the presence of arsine and an organometallic source, GaAs is selectively deposited only on areas of the substrate exposed to the laser at substrate temperatures in the range of 300–400° C. LCVD of undoped, n-type, and p-type device quality GaAs has been demonstrated. The laser-grown undoped GaAs films are highly resistive/semi-insulating (ρ=10⁶ Ωcm) and exhibit 77K photoluminescence (PL) spectra. Selective p-type doping (Zn from dimethylzinc, p > 10²⁰ cm^-3) has been achieved at substrate bias temperatures (T_sub) of 300°C. Selective and controllable n-type doping (Si from silane, ~ 10¹⁷ ≤ n ≤ 7×10¹⁸cm^-3) has been demonstrated for 300 ≤ T_sub ≤ 400°C with room temperature mobilities between 600 – 5100 cm²/V sec. Several electronic and optoelectronic devices such as GaAs metal-semiconductor field-effect transistors (MOSFET’s), p-i-n photodiodes and metal-semiconductor-metal (MSM) photodetectors have been selectively deposited by the LCVD growth technique. These devices have performance characteristics comparable to devices of similar dimensions grown by conventional techniques. Rib, strip-loaded, and channel optical waveguides have also been directly written by LCVD. The mode structure and light confining properties of these waveguides have been studied.