Porous silicon: luminescence properties
Porous silicon (P-Si) became known for the first time in 1956 in a publication by A. Uhlir, in which the material was obtained as a byproduct of photoelectrochemical etching of holes in the plates of crystalline silicon (Uhlir, 1956). Two years later, D. Turner (Turner, 1958) examined in more detail and described P-Si as a special kind of silicon formed by electrochemical etching of monocrystalline silicon (c-Si). After that, there was a lull in the studies of P-Si for almost thirty years, which was only occasionally broken by individual works. For example, in 1984 researchers at the British Royal Institute for Radar and Communication observed photoluminescence (PL) of P-Si in the visible spectrum at the liquid helium temperature (Pickering et al,1984). A detailed study of the properties of P-Si started after the discovery by L. Canham at the British Defense Research Agency of efficient photoluminescence of this material at room temperature (Canham et al, 1990). In his paper he proposed an interesting hypothesis that the PL in P-Si is related to the quantum size effect for charge carriers. Almost simultaneously a conclusion on the possibility of the quantum size effect in P-Si was proposed by Gössele and Lehmann who analyzed the mechanism of formation of this material (Lehmann & Gössele, 1991). By the time these pioneering works were carried out attention was already paid to the production, exploration and application of nanostructures, starting from quantum wells to quantum dots of various semiconductors. In this connection there was a tempting prospect of using a fairly simple way to obtain P-Si for the formation of silicon quantum wires and dots, which could then be used to create light-emitting silicon devices. But it has not yet been possible to achieve full success in the practical application of the light-emitting properties of P-Si because of the insufficiently high photoluminescence quantum yield.