Observation of pn-junction depth in Mg₂Si diodes fabricated by short period thermal annealing

Abstract

We have fabricated Mg2Si pn-junction diodes by short-period (30 sec and 1 min) annealing between 400 ℃ and 480 ℃ and evaluated the pn-junction depth by EBIC and VC observations. The pn-junction depth of approximately 6 and 30 µm was formed for the annealing conditions of 400 ℃, 30sec and 480 ℃, 1min, respectively. By comparing the Ag depth profiles determined by SIMS, we estimated the activation ratio at the pn-junction of approximately 8 and 10 % for annealing at 450 ℃ and 480 ℃, respectively. All diodes showed clear rectifying behavior in J-V characteristic and the spectral photosensitivity below approximately 1.8 µm under zero bias condition.

Growth of 2-inch diameter Mg₂Si crystal by the VGF method under Ar normal pressure

“…Magnesium half-silicide (Mg2Si) is an interesting semiconducting material suitable for mass production because its constituent elements are abundant in the earth's crust, inexpensive, and have low toxicity. Mg2Si p-n-junction photodiodes have attracted considerable attention as inexpensive optical detectors in the short-wavelength infrared region [1][2][3][4][5][6][7][8] because of their indirect bandgap energy (0.61 eV) at room temperature [1][2]. Bulk single crystals with low electron concentrations have been developed using the vertical Bridgman (VB) method [1,3], and the p-n junction was directly fabricated onto the n-type substrate by simple thermal diffusion [2,[4][5].…”