Preparation and characteristics study of CuAlO₂/Si heterojunction photodetector by pulsed laser deposition

P-type copper aluminate CuAlO₂ thin film was deposited on glass and silicon substrates by using pulsed laser deposition technique to fabricate CuAlO₂ heterojunction photodetector without using any post-deposition annealing. The structural, optical and electrical properties of CuAlO₂ film were investigated. X-ray diffraction XRD pattern showed that the diffraction peaks are assigned to crystalline CuAlO₂ of rhombohedral crystal structure. UV–Vis sprctrophotometeric measurement showed that average optical transmission of 80% can be reached and the optical direct and indirect band gap values were found to be 3.6 and 2.1 eV, respectively. The photoluminescence PL investigation showed the emitting peak is centered at 390 nm corresponds to 3.52 eV, which is close to the optical band gap. Scanning electron microscopy SEM investigation revealed that the film consists of some of agglomerated particles having size in the range of 75 nm −1 μm. EDX analysis shows that the deposited film has small-off stoichiometry .The electrical and photoresponse properties of anisotype p-CuAlO₂/n-Si and isotype p-CuAlO₂/p-Si heterojunction photodetectors fabricated without using buffer layer were measured and analyzed. The heterojunctions exhibited good rectifying characteristics. The spectral response of p-CuAlO₂/n-Si photodetector showed maximum value of responsivity approaching 541 mA/W corresponding quantum efficiency of 90% at750nm under 2.5 V bias voltage.