Selective dry etching of GaAs/AlOx for realizing electrical isolation on monolithic integrated photonic crystal laser array

Abstract

Extremely high etch selectivity of GaAs over AlOx is mandatory to fabricate a current blocking trench (CBT) between adjacent lasers in a photonic crystal (PhC) laser array for intra-chip optical interconnections. In this paper, selective etching of GaAs on AlOx with PhC structure is reported for the first time by using inductively coupled plasma etching with Cl2/BCl3-containing gas mixture. The etched profile of the CBT on GaAs/AlOx heterostructure with PhC structure was significantly different from that without PhC structure. By optimizing the etching conditions, the etching of the CBT was stopped at AlOx, and extremely high etch selectivity of GaAs over AlOx was achieved. Thus, we successfully fabricated the CBT in the PhC laser array. The horizontal electrical resistance between adjacent laser cavities with a 0.4 μm or wider CBT reached the instrumentation-limit of 100 MΩ, confirming the electrical isolation effect of the CBT.