Porous Si Based Al Schottky Structures on p+-Si: A Possible Way for Nano Schottky Fabrication

Abstract

This paper presents the results of a comparison research between the Al/p-Si/Al, Al/p+-Si/Al and Al/PS/p+-Si/Al devices. The current transport mechanism of an Al/por-Si/p+-Si/Al heterojunction device with a porous silicon layer fabricated by the electrochemical anodization process has been investigated using temperature dependent current–voltage measurements in the temperature range of 10–300K, and these measurements are realized even for Al/p-Si/Al diode. The porosity properties of porous Si layer are investigated by a cross-sectional SEM view and a PL measurement. The good rectification for a Schottky like diode which was formed by Al metallization of porous silicon (PS) on p+-Si substrate was observed and it continues even in 6K temperature, despite Al/p-Si/Al diode freezing out at 20K. Moreover, it is reported that the Al/PS/p+-Si/Al heterojunction device reveals the excellent junction parameters with an ideality factor very close to unity, a high barrier height which is 0.63eV and a small value of series resistance that is 30Ω, at 300K. However, the high serial resistance values for this heterojunction device compared to that of the crystalline Si based on the Al/p-Si/Al diode are related to PS. At high temperatures, it is noted that the current transport mechanism is through the thermoionic-field emission mechanism. However, at low temperatures, the unreliable variation of the Richardson plot is seen, and no distinct Gaussian distribution is seen in the relation of Φb vs. q/2kT; and this behaviour is attributed to the highly doped silicon. Furthermore, in this study, the current transport mechanism is discussed by using the Fowler Nordheim tunnelling theory in PS, and it is proposed that tunnelling via the migration/diffusion is the main mechanism of charge transport in PS.