The role of aluminum in selective reactive ion etching of GaAs on AlGaAs

Abstract

We have studied the role of aluminum in the formation of an etch barrier at the GaAs/ Alx Ga1−x As interface during reactive ion etching in CCl2 F2 plasma. The minimum Alx Ga1−x As thickness needed to form the barrier is Al mole fraction dependent and was determined with etching experiments monitored by optical emission spectroscopy. Effective Alx Ga1−x As layers for forming an etch barrier are 275 Å for x=0.02, 22 Å for x=0.10, 15 Å for x=0.15, 12 Å for x=0.20, and 9 Å for x=0.30. For all Al mole fractions except x=0.02, these thicknesses correspond to a sheet dose equivalent to 3/4 of a monolayer of Al in the original Alx Ga1−x As layer. Barrier layers for x=0.02, 0.10, 0.25, and 0.30 were examined without air exposure by angle-dependent x-ray photoelectron spectroscopy. For samples that are not overetched, the surface is covered with ∼20 Å of AlF3 intermixed with a gallium halide containing chlorine and fluorine and is depleted of arsenic. For substantially overetched barriers, a 30 Å layer is formed with gallium halide present at the surface, AlF3 found farther in, and arsenic depletion throughout the barrier. During extreme overetch, barrier layers on the order of tens of Å in thickness were not etched away and yet did not completely prevent very slow etching of underlying GaAs. Barrier layers on the order of 60 Å in thickness did prevent etching of underlying GaAs. Collectively the data suggest that the role of Al is formation of AlF3 exclusively and that only this compound is responsible for stopping the GaAs etch.

Dry etching of GaP with emphasis on selective etching over AlGaP

“…Selective etching has been achieved with various materials heteroepitaxially grown on GaAs, [1][2][3][4][5] InP, 6,7 InAs, 8 and GaN ͑Refs. Photonic devices such as vertical cavity surface emitting lasers, transport devices such as heterojunction bipolar transistors, and even microelectromechanical systems require the capability of etching and selective etching.…”

“…[1][2][3][4] In reactive ion etching ͑RIE͒, chlorine-based gasses are effective etchants of both GaAs and AlGaAs because of the formation of volatile compounds GaCl 3 , AlCl 3 , and AsCl 3 . This etch chemistry has been used to demonstrate a selectivity of GaAs over AlGaAs as high as 500.…”

Characterization of Plasma-Induced Damage of Selectively Recessed GaN/InAlN/AlN/GaN Heterostructures Using SiCl4and SF6

“…Chlorine and fluorine gas mixtures have been extensively used in fabrication of III-N-based devices. Chlorine is very effective in etching Ga, In, and Al 21) whereas the incorporation of fluorine leads to less volatile etch products (AlF 3 , 22) GaF 3 , InF 3 ), which can be used as etch-resistant barrier. Among them, AlF 3 has the strongest ionic bonding with a difference in electronegativity between Al and F of 2.39.…”

Selective metalorganic reactive ion etching of molecular-beam epitaxy GaAs/AlxGa1−xAs

“…Current selective reactive ion etching (RIE) of GaAs over AtGa l xAs uses mixtures of CC1 2 F2 and He, sometimes with an addition of oxygen to produce the desired etch-stop, I 4 or SF 6' SiCI 4 , and He. 7 • S In this paper we report on the use of a CH 4 and Hz metalorganic reactive-ion etching (MORIE) processes for selective etching of GaAs over Al",Ga,_ xAs, as an alternative to the established gas mixtures listed above. This is analogous to the selective etching process ofSi over S10 2 , by controlling the C:H ratio of CF 4 and H2 ctchant gases.…”

“…This is analogous to the selective etching process ofSi over S10 2 , by controlling the C:H ratio of CF 4 and H2 ctchant gases. Second, CH 4 and Hz etched GaAs exhibits low electrical damage as measured by the Schottky diode ideality factor. We use the term MORIE 9 ,10 in this paper to distinguish the process from the chlorine and fluorine RIE processing, as there are a number of major differences between the two processes.…”