Visible photoluminescence in porous GaAs capped by GaAs

A typical porous structure with pores diameters ranging from 10 to 50 nm has been obtained by electrochemical etching of (1 0 0) heavily doped p-type GaAs substrate in HF solution. Room temperature photoluminescence (PL) investigations of the porous GaAs (π-GaAs) reveal the presence of two PL bands, I1 and I2, located at 1.403 and 1.877 eV, respectively. After GaAs capping, the I1 and I2 PL bands exhibit opposite shift trends. However, the emission efficiency of these two bands is not strongly modified. Low temperature PL of capped porous GaAs versus injection levels shows that the I1 PL band exhibits a red shift while the I2 PL band exhibits a blue shift with increasing injection levels. The I2 PL band intensity temperature dependence shows an anomalous behaviour and its energy location shows a blue shift as temperature increases. The observed PL bands act independently and are attributed to electron - hole recombination in porous GaAs and to the well-known quantum confinement effects in GaAs nanocrystallites. The I2 PL band excitation power and temperature dependencies were explained by the filling effect of GaAs nanocrystallites energy states.