Epitaxial lift-off process for gallium arsenide substrate reuse and flexible electronics

Epitaxial lift-off process enables the separation of III–V device layers from gallium arsenidesubstrates and has been extensively explored to avoid the high cost of III–V devices by reusing the substrates. Conventional epitaxial lift-off processes require several post-processing steps to restore the substrate to an epi-ready condition. Here we present an epitaxial lift-off scheme that minimizes the amount of post-etching residues and keeps the surface smooth, leading to direct reuse of the gallium arsenide substrate. The successful direct substrate reuse is confirmed by the performance comparison of solar cells grown on the original and the reused substrates. Following the features of our epitaxial lift-off process, a high-throughput technique called surface tension-assisted epitaxial lift-off was developed. In addition to showing full wafer gallium arsenide thin film transfer onto both rigid and flexible substrates, we also demonstrate devices, including light-emitting diode and metal-oxide-semiconductor capacitor, first built on thin active layers and then transferred to secondary substrates.

Figure 1Concept of epitaxial lift-off (ELO) process and post-ELO GaAs surface morphologies with conventional and novel ELO processes.

Concept of epitaxial lift-off (ELO) process and post-ELO GaAs surface morphologies with conventional and novel ELO processes.

(a) Schematic illustration of general ELO process. (b,c) Schematic illustrations of the chemical reactions near the sacrificial layer/etchant interfaces during the conventional and the novel ELO process and the three-dimensional AFM ima…

Figure 2Surface morphologies of GaAs surfaces during ELO process.

Surface morphologies of GaAs surfaces during ELO process.

(a) AFM images of the GaAs substrate surface dipped in both concentrated and dilutedHF and HCl for 1 day. (b,c) are the schematic illustrations of the surface chemistry of GaAs dipped in HF and HCl, respectively.

Figure 3Performance of single junction GaAs solar cells fabricated on new and reused substrates.

Performance of single junction GaAs solar cells fabricated on new and reused substrates.

(a) Current density versus voltage (J–V) characteristics of GaAs SJ solar cells grown and fabricated on new (green symbols) and reused (blue symbols) substrates. Inset: solar cell performance parameters. (b) EQE of solar cells grown on…

Figure 4Surface tension-assisted ELO process.

Surface tension-assisted ELO process.

(a) Schematic illustration of the surface tension-assisted (STA) ELO process. (b) Etching rate of InAlP in HCl as the function of crystallographic direction. The maximum etching rate locates at <100>. All the data were normalized by max…

Figure 5GaAs thin films transferred to rigid and flexible substrates.

GaAs thin films transferred to rigid and flexible substrates.

(a) Demonstrations of the transferred GaAs thin films to the rigid Substrate (left, GaAs on 4″ Si wafer. Center, GaAs on curved solid object. Right, GaAs on glass) and (b) flexible substrates (left, GaAs on tape. Right, GaAs on flexible…

Figure 6Demonstration of transferred devices via novel ELO process.

Demonstration of transferred devices via novel ELO process.

(a) Transferred 2″ AlGaAs LED on 2″ Si wafer and the optical image of light emission. Scale bar, 5 cm. (b) Capacitance–Voltage (C–V) characteristics of n-GaAs MOSCAP before and after being transferred to a flexible tape. Inset: the opti…

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