Observation of the atomic surface structure of GaAs(001) films grown by metalorganic vapor-phase epitaxy

Mechanism of Arsine Adsorption on the Gallium-Rich GaAs(001)−(4 × 2) Surface

“…Scanning tunneling micrographs were obtained at a sample bias of -2.0 to -4.0 V and a tunneling current of 0.5 nA. 3 Arsine was introduced into the chamber at 5 × 10 -7 torr through a precision leak valve. Dosing was continued for up to 65 min to ensure that a constant coverage was obtained.…”

“…Then, the rates of arsine adsorption (r a ), arsine desorption (r d ), arsine surface reaction (r f ), and hydrogen desorption (r s ) are expressed by Here, [M] is the arsine concentration in the gas (molecules/ cm 3 ); V is the mean molecular velocity of arsine (cm/s); S 0 is the initial sticking probability of arsine; [D] is the density of adsorption sites, equal to 6.26 × 10 14 (sites/cm 2 ); and φ and θ are the fractional coverages of AsH 3 and AsH x species (x ) 1, 2), respectively. The term (1 -θ -φ) corresponds to the fractional coverage of gallium sites.…”

“…The term (1 -θ -φ) corresponds to the fractional coverage of gallium sites. In eq 9, it is assumed that the surface reaction rate is proportional to the coverage of adsorbed AsH 3 and AsH x intermediates. By including the latter term, we can account for the acceleration of the rate of arsine adsorption with time (cf.…”

“…The active layers in these devices are grown on the (001) plane of gallium arsenide by metalorganic vapor-phase epitaxy (MOVPE). [1][2][3][4][5][6][7][8][9][10] In this process, volatile precursors of the group III and group V elements in a hydrogen carrier gas are fed into a reactor containing a substrate heated to between 773 and 923 K. [1][2][3] The precursors adsorb and decompose on the wafer surface, depositing a single-crystal film that is lattice-matched to the GaAs substrate. The film surface plays a crucial role in this process, because it mediates the decomposition of the group III and group V reagents.…”

Gallium arsenide and indium arsenide surfaces produced by metalorganic vapor-phase epitaxy

“…This is because MOVPE growth is carried out at 10-760 Torr, where only photon-based techniques for in situ surface analysis may be used. However, we have recently developed an apparatus that integrates MOVPE reactor with an ultrahigh vacuum surface analysis system [9][10][11]. This apparatus has allowed us to characterize the structure and composition of film surfaces as they evolve during growth.…”