Wafer scale III-nitride deep-ultraviolet vertical-cavity surface-emitting lasers featuring nanometer-class control of cavity length

III-nitride AlGaN-based deep-ultraviolet vertical-cavity surface-emitting lasers (DUV-VCSELs) have shown a great application potential in optical atomic clock, maskless photolithography, etc. Nevertheless, the detuning issue owing to the uncontrolled cavity length, i.e. the difference between the resonance wavelength and gain peak, severely impairs the device performance. Herein, a DUV-VCSEL strategy featuring the uniform nanometer-class control of the cavity length in a 4 inch wafer is proposed in the DUV framework based on GaN templates, which ensures the wafer-scale removal of the sapphire substrates by laser lift-off, and then provides space for the subsequent deposition of dielectric distributed Bragg reflector (DBR). It is more significant that the strategy brings about a GaN/AlGaN sharp interface with an Al composition difference up to 80%, whereby self-terminated etching with an ultrahigh selectivity of 100:1 is achieved. The cavity length can hence be accurately determined by epitaxy itself instead of fabrication process, so as to minimize the detuning. As such, 285.6 nm optically pumped DUV-VCSELs with double dielectric DBRs are fabricated, exhibiting a record low threshold of 0.38 MW/cm ² as well as a narrow linewidth of 0.11 nm. What’s more, the lasing wavelength varies within 1.9 nm across the 4 inch wafer, indicating a cavity length variation of only 0.81%. This work establishes a promising strategy for III-nitride DUV-VCSELs, which will definitely speed up the development of devices featuring high performance and scalability.