Dual sacrificial layer strategy for effective release of InP materials with smooth surface for transfer printable devices

We present a detailed study of dual sacrificial layer structures comprising lattice-matched AlInAs and InGaAs for the efficient release of InP-based materials. The study aims to optimize surface smoothness and etch rate for transfer printing via direct bonding. This layer, combined with appropriate thicknesses, yields an extremely smooth coupon surface after release. At room temperature, we demonstrate an isotropic etch profile along with high selectivity to InP. The thickness of the release layers and dilution of the FeCl₃ mixture were optimized. We show that FeCl₃ and water (1:5) undercut a combined 400 nm InGaAs - 100 nm AlInAs release structure with 50% higher selectivity to InP compared with a 1:2 dilution. Such fast release with a smooth interface at room temperature yields an energy-efficient, cost-effective, and time-saving process contributing to superior printing.