Growth of high Bi concentration GaAs_1−xBi_x by molecular beam epitaxy

Abstract

The incorporation of Bi is investigated in the molecular beam epitaxy growth of GaAs 1Àx Bi x. Bi content increases rapidly as the As 2 :Ga flux ratio is lowered to 0.5 and then saturates for lower flux ratios. Growth under Ga and Bi rich conditions shows that Bi content increases strongly with decreasing temperature. A model is proposed where Bi from a wetting layer incorporates through attachment to Ga-terminated surface sites. The weak Ga-Bi bond can be broken thermally, ejecting Bi back into the wetting layer. Highly crystalline films with up to 22% Bi were grown at temperatures as low as 200 C. V

Novel Dilute Bismide, Epitaxy, Physical Properties and Device Application

“…A careful control of the As 2 :Ga flux ratio is essential to achieve a high Bi content and to avoid formation of Ga droplets. [136]. The Bi content is measured using high-resolution X-ray diffraction (HRXRD) and a similar behavior can be seen from the three data sets.…”

“…The strong segregation effect of Bi at a high temperature demands a low growth temperature for GaAsBi. Indeed, Bi incorporation is found to increase with decreasing growth temperature and the highest Bi content of 22% is achieved at the lowest growth temperature of 200 • C [136]. A sharp decrease of Bi content at growth temperature above 350 • C ocurres which is interpreted as strong Bi desorption at high temperatures.…”

“…In the second process an incorporated Bi atom is attached by a free Ga atom, thus the surface Bi content being reduced. This term was neglected in Lewis' paper [136] as they claimed that it was a minor effect compared with the first and the third process. The third process represents the incorporated Bi atoms are thermally ejected back onto the surfactant layer.…”

“…Lu's model is thus no longer valid as it has obeyed the major premise that the growing surface is group-V terminated. Based on the above argument, a new growth model is proposed by Lewis' et al [136] to account for Bi incorporation when the As:Ga flux ratio is~1.…”

Unexpected bismuth concentration profiles in metal-organic vapor phase epitaxy-grown Ga(As1−xBix)/GaAs superlattices revealed by Z-contrast scanning transmission electron microscopy imaging

“…Ga(As 1−x Bi x ) alloy material with Bi concentration as high as x = 0.22 has been reported for films grown using molecular beam epitaxy, 6 though values between 0.020 and 0.100 are more typical. [7][8][9] Substantial progress also has been made in the growth of Ga(As 1−x Bi x ) alloys by metal-organic vapor phase epitaxy (MOVPE).…”