Germanium Thin Film Formation by Low‐Pressure Chemical Vapor Deposition

Abstract

Thin films of polycrystalline germanium were formed by the pyrolysis of germane gas in a low-pressure reactor. Process parameters investigated were deposition temperature in the range 250 to 350°C and pressure in the range 300 to 600 mTorr. The properties of the film have been characterized using transmission electron microscopy and x-ray diffraction for structural analysis, atomic force microscopy for surface morphology analysis, secondary ion mass spectroscopy for compositional analysis, and Hall effect measurement for electrical parameter extraction, etc. High Hall effect mobility on the order of 300 cm2/V s was obtained, even at a relatively low deposition temperature of 300°. This makes the germanium thin films potentially very promising for low-temperature device processing. ABSTRACT Thin films of polycrystalline germanium were formed by the pyrolysis of germane gas in a low-pressure reactor. Process parameters investigated were deposition temperature in the range 250 to 350°C and pressure in the range 300 to 600 mTorr. The properties of the film have been characterized using transmission electron microscopy and x-ray diffraction for structural analysis, atomic force microscopy for surface morphology analysis, secondary ion mass spectroscopy for compositional analysis, and Hall effect measurement for electrical parameter extraction, etc. High Hall effect mobility on the order of 300 cm2/V s was obtained, even at a relatively low deposition temperature of 300°. This makes the germanium thin films potentially very promising for low-temperature device processing.

Low-temperature growth of polycrystalline Ge thin film on glass by in situ deposition and ex situ solid-phase crystallization for photovoltaic applications

“…[18], which suggested that preferential Ge (1 1 1) orientation is usually observed in poly-Ge films with large grain size while preferential Ge (2 2 0) orientation is usually observed in mc-Ge films with grain size with dimensions of several tens of nanometers. This point of view is supported by the extremely strong dominant (1 1 1) peak orientation observed in reference [19], where Ge films having >1 mm grain size were reported and also by experiments in reference [20]. The pronounced (1 1 1) orientation of our Ge thin films prepared by PVD is comparable to RF sputtered films on glass deposited at 600 8C with a similar thickness [6] or evaporated 400 nm thick Ge films on Si 3 N 4 CVDcoated Si substrate at 400 8C followed by annealing at 900 8C [4].…”

Atmospheric pressure metal organic chemical vapor deposition of thin germanium films

“…With respect to the morphology, the AFM images of films show a characteristic grain size (Fig. 7), which reaches from a few to 200 nm depending on the deposition temperature and is similar to that observed for germanium films deposited by low pressure CVD or epitaxy [27,54,70]. As the deposition temperature increases, an increase in the diameter of the individual grains at the surface is observed.…”

“…Germanes such as GeH 4 [51,52], Ge 2 H 6 [53], or germanium itself, as used in electron beam evaporation or in the PVD process, belong to the compounds of the first group. They can be used to deposit high-purity films [36,54] which hold potential in sensor [35] and semiconductor applications [36,37]. The germanes are widely used for the deposition of films despite their high sensitivity to oxygen and water and the necessary high safety precautions.…”

Intrinsic energy band alignment of functional oxides

“…10 Gallium‐doped germanium has been mainly synthesised by ion implantation,9, 10 whereas germanium and Si x Ge 1− x thin films are usually synthesised by using pulsed laser deposition (PLD) and chemical vapour deposition (CVD) 11. 12 In comparison, electrodeposition is a relatively simple process to deposit semiconductor thin films without the need for high temperature and vacuum. Recently, by using an electrochemical liquid–liquid–solid process (EC‐LLS), germanium could be deposited from aqueous solutions into a mercury pool 13.…”