Physica E 25 (2005) 636–642 Visible photoluminescence in porous GaAs capped by GaAs L. Beji a , L. Sfaxi b,Ã , B. Ismaı¨l b , A. Missaoui a , F. Hassen b , H. Maaref b , H. Ben Ouada a a Laboratoire de Physique et de Chimie des Interfaces, Faculte´des Sciences de Monastir, 5019 Monastir, Tunisie b Laboratoire de Physique des Semiconducteurs et des Composants Electroniques, Faculte´des Sciences de Monastir, Bd Environnement 5019 Monastir, Tunisie Received 2 March 2004; received in revised form 15 May 2004; accepted 15 September 2004 Abstract A typical porous structure with pores diameters ranging from 10 to 50nm has been obtained by electrochemical etching of (100) heavily doped p-type GaAs substrate in HF solution. Room temperature photoluminescence (PL) investigations of the porous GaAs (p-GaAs) reveal the presence of two PL bands, I 1 and I 2 , located at 1.403 and 1.877eV, respectively. After GaAs capping, the I 1 and I 2 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 I 1 PL band exhibits a red shift while the I 2 PL band exhibits a blue shift with increasing injection levels. The I 2 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 I 2 PL band excitation power and temperature dependencies were explained by the filling effect of GaAs nanocrystallites energy states. r 2004 Elsevier B.V. All rights reserved. PACS: 68.37.Lp; 81.07.Vb; 82.45.+z; 81.60.Cp Keywords: Porous GaAs; Molecular beam epitaxy; Photoluminescence; Quantum confinement 1. Introduction The great interest in exploiting the unique properties of porous silicon in device applications has opened new research fields for investigating porous layers in other semiconductor materials. Among them, GaAs is of great interest because ARTICLE IN PRESS www.elsevier.com/locate/physe 1386-9477/$-see front matter r 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.physe.2004.09.005 Ã Corresponding author. Tel.: +21698403862; fax: +21673500278. E-mail addresses: lotbej_fr@yahoo.fr, lotfi.beji@fsm.rnu.tn (L. Beji), larbi.sfaxi@fsm.rnu.tn (L. Sfaxi).