Laser light sources emitting in the deep ultraviolet wavelength range between 210 and 230 nm are of great interest for spectroscopic applications. Here, a compact DUV diode laser system emitting at a wavelength of 222.5 nm is presented. The system is based on frequency doubling of the laser radiation from a micro-integrated GaN external cavity diode laser module (μECDL) emitting at 445 nm. The μECDL has an optical pump power of 1.4 W with an emission bandwidth of 35 pm. Narrowband laser radiation in continuous wave operation with an output power of 160 μW at 222.5 nm is generated in a single-pass frequency doubling stage with a β-BaB2O4 crystal. The results are suitable to address applications such as spectroscopic investigations of biological samples. The presented concept of a compact and efficient deep ultraviolet laser light source enables the realization of portable systems for which a small footprint and a low power consumption is essential.