Large area surface micro-structuring is most commonly used to reduce the reflection loss and improve the light absorption in solar cells, photo-detectors and image sensors. Herein, chemically prepared textured GaAs with improved absorption in the entire range of the solar spectrum is investigated using UV–Vis–NIR spectrometer, showing that an average specular reflectance can be reduced to ~ 0.2% in the wavelength range of 3000–300 nm. The sputtered MoO 3 thin film (10 nm) on textured GaAs further reduces the reflection loss down to ~ 0.1% (average value) in same wavelength range, i.e., 300–3000 nm. The phase, morphology, composition, and transport properties of the thin films were investigated using XRD, SEM, AFM, XPS, and Keithley source meter, respectively. SEM and AFM scanning show highly ordered elongated microstructure has been induced on pristine GaAs substrate after wet chemical etching. XRD analysis shows amorphous nature of the MoO 3 thin film. In addition, XPS studies confirm that MoO 3 thin film present on the surface of textured GaAs. Moreover, hole-blocking property of the MoO 3 thin film has been studied with the help of Anderson model. Further, current–voltage characteristics (under dark condition) show rectifying behavior of the heterojunction (Ag/MoO 3 /GaAs/Ag). Hence, the present study is not only important for the basic understanding of charge transports across the heterojunction, but also to also to design hole-blocking-based solar cell.