Effect of carrier concentration on optical bandgap shift in ZnO:Ga thin films

The Ga-doped ZnO thin films were deposited on glass substrate by sputtering and annealed at 350 °C in hydrogen atmosphere for 1 h. The optical bandgap of thin films showed the lower blueshift than the theoretical value of the Burstein–Moss (BM) effect. The shift of bandgap was dependent on the carrier concentration and acquired by combining the nonparabolic BM effect and bandgap narrowing (BGN). The modified BM effect equation was proposed to substitute the nonparabolic BM effect and BGN. The exponent in the modified BM equation was affected by carrier concentration and it was decreased with carrier concentration.