Post-growth technology of multi-junction photovoltaic converters based on A$^3$B$^5$ heterostructures

Investigation and development of the post-growth technology for fabricating multi-junction photovoltaic converters based on GaInP/GaInAs/Ge heterostructure has been carried out. Antireflection coating, ohmic contacts and mesa- structure forming stages have been reviewed. The technology of $n^+$-GaAs contact layer etching with the help of plasma-chemical, liquid and ion-beam etching has been investigated. Antireflection coefficient of radiation from the heterostructure with TiO$_x$/SiO$_2$ ($x$ close to 2) antireflection coating surface was less then 3% in wavelength range 450–850 nm. The value of contact resistance for $n$- and $p$-type conductivity was 3$\cdot$10$^{-5}$–3$\cdot$10$^{-6}$ $\Omega$cm$^2$, the decrease of photosensitive region shading degree at increased bus-bar conductivity has been archived. The mesa-structure surface current leakage decreased to the value of 10$^{-9}$ A at voltage less then 1 V.