Nonlinear Kinetics of GaAs MOVPE Examined by Selective Area Growth Technique

Abstract

Two-dimensional or three-dimensional numerical simulation on growth rate nonuniformity of selective area metallorganic vapor phase epitaxy ͑SA-MOVPE͒ in sub-millimeter scale can extract real surface kinetics, which is normally hindered by mass transport rate of film precursors. Nonlinear surface kinetics is introduced to analyze group-III precursor concentration dependency of SA-MOVPE for the first time and surface reaction rate constant ͑k s n ͒ of adsorbed species and adsorption equilibrium constant ͑K͒ are extracted from GaAs-MOVPE at 575°C. The effect of misorientation angle ͑͒ of GaAs͑100͒ substrate on these kinetic parameters was examined. It was found that k s n is about 3.4 ϫ 10 −5 mol m −2 s −1 independent of , whereas K ranged from 6.9 to 12 ϫ 10 5 m 3 mol −1 dependent on . The obtained value of k s n can be converted to lifetime of adsorbed species on GaAs surface and it is 0.3 s. This is mostly the same with gas-phase decomposition rate of trimethylgallium and supports the accuracy of our nonlinear kinetic analysis.Metallorganic vapor phase epitaxy ͑MOVPE͒ is a wellestablished growth method for the fabrication of III-V compound semiconductor materials and devices, such as laser diodes, optical switches, and optical amplifiers. 1,2 It is particularly adaptable for mass production and devices requiring large areas. The device properties can be controlled through designing the material structures in the bulk, interface, and surface. To obtain the desired material structures, and hence the desired device properties, growth process should be precisely controlled. However, MOVPE process is very complicated due to the heat and mass transfer both in the gas-phase and surface, and there are no invariable growth conditions suitable for all the reactors for required material structures. Therefore, much trial-and-error is needed to optimize empirically the growth conditions. 3 A slight change in the precursor or reactor necessitates reoptimization, which wastes a large amount of resources. To improve the present situation, it would be useful to analyze and model MOVPE process. The processes in the gas-phase of MOVPE are reasonably able to be well understood, 4,5 however the processes on the growing surface are not. 6 Therefore, investigation on the surface reaction has been one of the basic topics for MOVPE technique. 7-9 Although kinetic Monte Carlo method can be used to simulate chemical reaction paths on surface, 10 a simple experimental analytical method will save computer cost and time.Selective area growth ͑SAG͒ in MOVPE is very useful for one step fabrication of optoelectronic integrated circuits. [11][12][13][14] In SAG, the substrates are partially covered by dielectric masks such as SiO 2 or Si 3 N 4 . Because there is no growth taking place on the masks during the epitaxial growth, the reactants will be accumulated above the masks and result in higher concentration compared with the selective growth region. Lateral vapor phase diffusion from above the masks area and surface migration would be responsib...

Non-linear surface reaction kinetics in GaAs selective area MOVPE

“…Therefore in an earlier report [4], non-linear surface reaction kinetics based on the Langmuir-Hinshelwood model, revealing the intrinsic mechanism in MOVPE, has been suggested to GaAs growth at 575 1C. Two kinetic parameters, surface reaction rate constant in non-linear kinetics (k s n ) and adsorption equilibrium coefficient (K), are extracted and examined at different substrate misorientation angle [4]. As a sequential study, in this paper, these non-linear kinetic parameters, k s n and K, for GaAs SAG-MOVPE are investigated at varied growth temperature 520-650 1C.…”

“…In our group, a two-dimensional (2-D) numerical simulation method has been developed to deduce the kinetic process during SAG-MOVPE [3,4] giving a quantitative analysis for kinetic parameters. And the effect of growth conditions on those parameters has been examined systemically.…”

“…Linear and non-linear kinetic analysis in MOVPE by the way of SAG technique has been developed in our group few years ago to understand the growth mechanism in InGaAsP-related compound [3,4]. This kind of analysis is potentially useful to overcome the drawback in traditional ''trial-and-error'' method for the manufacture of OEICs by SAG, because it is possible to predict the distributions of growth rate, composition, hence the properties through the kinetic analysis prior to making growth [5].…”

“…Surface reaction rate constant in linear kinetics (k s l ) can be extracted, which depends on growth conditions. In previous research, we examined the dependencies of k s l of GaAs on growth temperature [3,6], substrate misorientation angle [6], group III and V partial pressures [4,7], position in the reactor [8], and doping process [9]. However, the dependency of k s l on group III partial pressure at low growth temperature casts doubt on linear kinetics.…”

“…However, the dependency of k s l on group III partial pressure at low growth temperature casts doubt on linear kinetics. Therefore in an earlier report [4], non-linear surface reaction kinetics based on the Langmuir-Hinshelwood model, revealing the intrinsic mechanism in MOVPE, has been suggested to GaAs growth at 575 1C. Two kinetic parameters, surface reaction rate constant in non-linear kinetics (k s n ) and adsorption equilibrium coefficient (K), are extracted and examined at different substrate misorientation angle [4].…”