High Quality P-Type Mg-Doped β-Ga2O3–δ Films for Solar-Blind Photodetectors

The ( $\overline {{2}} {01}$ )-oriented Mg-doped $\boldsymbol {\beta }$ - ${\text {Ga}}_{2}{\text {O}}_{3- \delta }$ films were grown on (0001)-sapphire substrates by pulsed laser deposition (PLD) at various oxygen partial pressures ( $\text{P}_{\text {O}}\,\,=10$ -40mTorr). The conductivity type of the as-deposited Mg-doped ${\beta }$ - ${\text {Ga}}_{2}{\text {O}}_{3- \delta }$ films is proved to be ${p}$ -type according to the transfer characteristic curves of a top-gate field effect transistor (FET) and rectification curves of the Mg-doped /undoped ${\beta }$ - ${\text {Ga}}_{2}{\text {O}}_{3- \delta }$ junction. In addition, the two-terminal solar-blind photodetectors based on Mg-doped ${\beta }$ - ${\text {Ga}}_{2}{\text {O}}_{3- \delta }$ films prepared at $\text{P}_{\text {O}} =30$ mTorr exhibite a good optoelectrical performance with a low dark current of 0.19 pA at 10 V, a high $\text{I}_{\text {254nm}}/\text{I}_{\text {dark}}$ ratio of ${1.3}\,\,\times \,\,{10}^{{4}}$ , fast rise ( ${\tau }_{\text {r1}} =0.035\text{s}$ and ${\tau }_{\text {r2}} =0.241\text{s}$ ) and decay ( ${\tau }_{\text {d1}} =0.022\text{s}$ and ${\tau }_{\text {d2}} =0.238\text{s}$ ) times. The present work indicates that the ${p}$ -type Mg-doped ${\beta }$ - ${\text {Ga}}_{2}{\text {O}}_{3- \delta }$ films can be used in the third-generation ultraviolet photodetectors.