Photo-atomic layer etching (photo-ALE) of GaAs and AlGaAs semiconductors was investigated in deionized H2O and aqueous solution of NH4OH under weak excitation conditions ( P ≈ 20 mW/cm2). The process is based on digital photocorrosion in a processed solution and a negligible corrosion during the light-off phase employed for dissolution of the photocorrosion products. An inductively coupled plasma mass spectroscopy (ICP-MS) analysis revealed that photo-ALE of GaAs in an aqueous solution of NH4OH proceeds linearly with the number of reaction cycles, typically at ∼0.1 nm/cycle, and with the light-off phase as short as 22 s sufficient to entirely dissolve the photocorrosion products generated during a 3 s irradiation. In agreement with the ICP-MS data, the constant photo-ALE rates in NH4OH were also demonstrated in situ with the photoluminescence measurements. Our results suggest that the congruent decomposition of III-V materials and the etching of deep structures with atomic layer resolution could be facilitated by switching in situ between different etching environments.
Keywords: GaAs/AlGaAs nanoheterostructures; atomic layer etching; compound semiconductors; digital photocorrosion; photoluminescence.