| || Luminescence from Porous Silicon
Author : Jain, V.K. ;Gupta, (Mrs) A.
Source : Defence Science Journal ; Vol:48(1) ; 1998 ; pp 61-68
Subject : 621.315.592 Semiconductors
Keywords : Fabrication process ;Light emission;Porous silicon;Electroluminescence;Photoluminescene
Abstract : Recent observations of photoluminescene (PL) and electroluminescence (EL) from porous silicon (PS) have prompted many theoretical and experimental studies. Bulk crystalline Si is an indirect band gap material in which recombination is dominated by non-radiative processes. Therefore, it cannot be used as light-emitting component in Si circuits. PS is a new material formed by anodisation of single crystal Si wafers in hydrofluoric (Hi) solution. Luminescence from this material is being explored for technological applications all over the world. The mechanism of luminescence is still not well-understood. Several models have been proposed but still the facts about the strong light emission at room temperature are unknown. This paper presents a review of the fabrication process and studies on luminescent properties of PS. A hybrid model based on quantum confinement of carriers in the nanometer size Si crystallites having a large number of surface states is suggested to explain the observed properties.
| || Effect of Different Chemical Environment on Porous Silicon
Author : Gupta, Amita;Jain, Alok;Jain, V.K.
Source : Defence Science Journal ; Vol:50(1) ; 2000 ; pp 87-94
Subject : 620.1 Material Science and Technology
Keywords : Porous silicon;Chemical vapours
Abstract : Properties of porous silicon (PS) are found to be sensitive towards different chemical environment. Because of its large surface area, it is highly reactive and can adsorb chemical vapours. The present study shows that photoconductivity and photoluminescence (PL) properties are changed significantly in the presence of acetone, ammonia and steam vapours and can be used to identify and sense these chemical environment. These results also suggest that the molecules adsorbed on the pores change the transport mechanism of carriers in PS, leading to increase or decrease in conductivity. On the other hand, surface states on the enormous PS surface are modified under different chemical environment, leading to change in visible PL.