Etching of GaAs(100) Surfaces by Halogen Molecules:  Density Functional Calculations on the Different Mechanisms

Abstract

Using density functional theory, reaction energies and related barrier heights are calculated for the chemisorption/desorption of X2, Ga2, As2, GaX n , and AsX n (n = 1−3, X = F, Cl, Br, and I) at GaAs(100) surfaces modeled by molecular clusters. The obtained data provide different reaction mechanisms for etching by halogen molecules and allow the interpretation of experimental findings. Under low F2 exposure, AsF and GaF are formed at and desorbed from the surface. The other halogen molecules cause the desorption of GaX and As2. The rate-limiting steps are the AsF and As2 removals, respectively. The I2-exposed surface can preferentially desorb iodine and, with that, stop the etching of GaAs(100) surfaces as found experimentally. Under high halogenation, strongly bound GaX2 and AsX2 as well as weakly bound GaX3 and AsX3 are found at the surface. The volatility increases for GaX3 from F to I. The volatility of AsX3 has a maximum for chlorine. AsBr3 and AsI3 hand over halogen atoms to the remaining Ga atoms of the second layer during desorption.

Franck–Condon simulation of the photoelectron spectrum of AsCl2 and the photodetachment spectrum of AsCl employing UCCSD(T)‐F12a potential energy functions: IE and EA of AsCl2

“…[1][2][3] Although different halogen atoms can be selected for known reactions at a semiconductor surface, the most frequently investigated etchant for GaAs surfaces is Cl 2 . [4][5][6][7][8] It has been found that the etching reaction of Cl 2 on GaAs surfaces occurs in a step-wise manner via AsCl, AsCl 2 , and AsCl 3 . 2,9 In addition, in a study on the adsorption and decomposition reactions of AsCl 3 on the gallium-rich GaAs(100)-(4 3 1) surface, the mass spectrum of the gas-phase arsenic trichloride, measured by directly pumping the vapor from the surface into the mass spectrometer, revealed a fragmen-of GaAs surfaces.…”

“…Computationally, a few density functional theory (DFT) studies have been carried out recently on adsorptions, desorptions, and reactions arising from etching of GaAs surfaces by Cl 2 . [4][5][6] However, to our knowledge, there was only one ab initio study on low-lying electronic states of AsCl 2 and its cation, which reported a calculated IE for AsCl 2 in 1997. 13 This is a CASSCF/MRSDCI investigation, which employed a relativistic effective core potential (RECP) and a contracted valence [3s3p2d] basis set for As.…”

Franck–Condon simulation of the photoelectron spectrum of AsF2 and the photodetachment spectrum of AsF2− using ab initio calculations: Ionization energy and electron affinity of AsF2

“…4 In this connection, arsenic fluorides have received some attention because of their importance in the semiconductor industry. [5][6][7] However, there have been very few spectroscopic and computational studies on AsF 2 , its cation and anion, and the ionization energy and electron affinity of AsF 2 are not well established. Specifically, there are three spectroscopic studies on, or related to, AsF 2 .…”

Nanoholes Formed by Au Particles Digging into GaAs and InP Substrates by Reverse Vapor–Liquid–Solid Mechanism

“…The etching rate was fast compared with GaAs; hole length reached 1 mm in 10 min at 440 C even though PH 3 was also supplied during the etching. For InP, the {111}B faces do not seem to block the etching, probably because the In-P bond is not strong enough, 9,10) which means the P can be removed easily also on the {111}B faces.…”