Band-to-Band and Band-to-Acceptor Photoluminescence Studies in InSe under Pressure

摘要

We report on photoluminescence (PL) measurements under pressure on p-type N-doped InSe at 10 #KAPPA# and on n-type Si-doped InSe at room temperature. Low-temperature PL of N-doped InSe is dominated by a band-to-acceptor peak. From the pressure dependence of the ionization energy of the N related shallow acceptor, the pressure change of the hole effective mass is estimated through the Gerlach-Pollmann model for hydrogenic levels in uniaxial crystals and discussed in the framework of a k.p model. Room temperature PL in Si-doped InSe is dominated by a band-to-band peak exhibiting a pressure shift in agreement with previous works. This PL peak has been measured up to 7 GPa and a steep reversible decrease of its intensity has been observed above 4 GPa. This decrease has been interpreted as a supplementary evidence of a direct-to-indirect gap crossover, already observed in other layered semiconductors.