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Nanoscale metal - semiconductor contact electrical characteristics

Author: SongJunQiang
Tutor: WangXun；CaiQun
School: Fudan University
Course: Condensed Matter Physics
Keywords: Nanodots Schottky contact Semiconductor contact Schottky barrier height Semiconductor Technology Ohmic contact Electrical Characteristics Forward bias Surface states Reverse bias Substrate Transmission characteristics Nanowires Nanostructured Barrier layer Thermionic emission theory Electrical Properties Effective barrier height Zero bias Surface effect
CLC: O472.4
Type: PhD thesis
Year: 2009
Downloads: 243
Quote: 0
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Abstract

Metal-semiconductor contact (ohmic contacts and Schottky contact) are all semiconductor electronic devices and optoelectronic devices, one of the core structure. As semiconductor devices are getting smaller, especially down to the nanometer scale, the need for these nano-depth study of the performance of the device. The nano-sized metal - semiconductor contact nanodevices research field is one of the directions. Preparation of the semiconductor surface of the metal nano-contact, because the current has good compatibility with microelectronic technology is widely concerned. Meanwhile, the rare earth metal silicide having a high electrical conductivity, on the N-type silicon having a low Schottky barrier, and on the P-type silicon has a high Schottky barrier. Thus, the silicide nanostructures nanometer semiconductor devices in the future, such as ohmic interconnections, optical devices, and so has a very important application value. In this thesis work, we study the erbium silicide silicon nano metal - semiconductor contacts Preparation and electrical properties. The main work and innovations are as follows: 1. Using in situ ultrahigh vacuum scanning tunneling microscope (UHV-STM) to achieve the Si (001) and Si (111) surface of erbium silicide nanostructures Morphology, by adjusting the coverage, annealing temperature and annealing time to achieve these three growth conditions erbium silicide nanostructure morphology and bulk structure of growth regulation. 750 ℃ ??high temperature annealing, the Si (001) surface was prepared having a tetragonal crystal structure and high-quality bait silicide interface nano-islands. These pre-pyramid-shaped nano-islands have a relatively wide size range in length from a few nanometers to hundreds of nanometers in width from a few nanometers to several tens of nanometers in height between 3-9 nm. Further to these nano surface of the substrate around the island for high-resolution STM image, results mainly from the Si substrate surface and Er chain dimers induced micro-structure. For the Si (111) surface of erbium silicide nanostructures STM study found that at low coverage Er (0.5 ML), by low temperature (lt; 600 ℃ and 700 ℃) continuous annealing, a length of 200-500 nm can be formed silicide erbium nanowires. The formation mechanism of these nanowires is completely different from the Si (001) surface of the nanowires erbium silicide formation mechanism - lattice mismatch mechanism but rather two-dimensional (2D) erbium silicide triangular island combined thermal power driven continuously cured results. At higher Er coverage (0.8 ML), by annealing at 700 ℃, the formation of three-dimensional (3D) and two-dimensional (2D) erbium silicide island. Continue after annealing at 750 ℃, decomposition of metastable 2DErSi2 island. Since Si (111) surface is formed in the island size is usually in the hundreds 3DErSi1.7 nm, and a relatively small size 2DErSi2 island is metastable, so we choose Preparation high Si (001) surface of the nano-islands erbium silicide As a nano-metal - semiconductor contact the object of study. (2) the use of in situ ultrahigh vacuum scanning tunneling microscope (UHV-STM) to achieve the erbium silicide nano-islands / p-Si (001) 纳米肖特基 study the electrical properties of the contact. By reducing the STM tip and the metal silicide contacts erbium islands, after which the scanning voltage, and the recording current, obtained erbium silicide islands / p-Si (001) nano-contact IV characteristics. Measurement results show that the erbium silicide contacts 纳米肖特基 still has rectification characteristics, but the current density macro erbium silicide Schottky contacts at least five orders of magnitude larger, and showed significant size-dependent, ie, the current density through contact with the reduce the contact area increases. Further studies showed that, erbium silicide contact 纳米肖特基 effective Schottky barrier height (0.28-0.32 eV) is much smaller than the macro erbium silicide Schottky barrier height of the contact (0.73 eV). Analysis showed tunneling and mirror is reduced leading to a reduced effective Schottky barrier may cause. However, we also found that in the experiment, erbium silicide contact 纳米肖特基 IV characteristics of the true narrow cavity is very sensitive to residual gas adsorption. Adsorbed on the surface after 24 hours after the effective Schottky barrier height can be increased by about 0.1 eV. This suggests that erbium silicide nano-Si surface states around the island on erbium silicide contact 纳米肖特基 IV characteristics are strongly affected. 3 Use the O2 and NH3 adsorption experimental study of erbium silicide 纳米肖特基 contact surface effect. O2 and NH3, respectively, using the erbium silicide nano-islands on Si substrate surface surrounding states were gradually corrected, research erbium silicide contacts 纳米肖特基 IV characteristics of the substrate surface state electricity characteristic dependence. Experimental results show that with the amount of O2 and NH3 adsorption increases in a reverse bias, a similar ohmic contact transmission channel is continually suppressed; while in forward bias, a similar diode is constantly suppressed transmission channel . This is indicated by surface states (or surface electronic properties) controlled current transmission channel, the performance of the reverse bias class ohmic contact transmission characteristics, and performance under forward bias diode of the transmission characteristics of the class. Further, based on the energy band bending theory, analyzes ErSi2 纳米肖特基 contact surface states around the physical mechanism of its impact. We recommend ErSi2 between the island and the Si substrate, there are three possible current path, ie the surface state band channel, surface and interfacial space charge layer channel space charge layer channel. Among them, the first two conductive paths affected by the electronic properties of the Si surface. In the reverse bias voltage, the current state of the surface with the main conduction path, the other two channels is high barrier channel; the forward bias, the three channels may have been effective current transmission channel. Our experimental results and theoretical analysis for further study of nano metal-semiconductor contact surface effect is important. 4 of erbium silicide impact of chemical instability. The gas adsorption experiments, we noticed ErSi2 Island prolonged exposure to oxygen and ammonia in the atmosphere will lead to its very soon, \As ErSi2 adsorption excess O2 and NH3 molecules, which constantly and ErSi2 reaction, leading to the STM tip and the contact resistance between the islands ErSi2 risen sharply, resulting IV measurement does not reflect the interface contact information and meaningless. Therefore, since erbium silicide easy \The method may be by other means to eliminate the surface effect, or select a metal having a high chemical stability to prepare nano-contact material.

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CLC: > Mathematical sciences and chemical > Physics > Semiconductor physics > Semiconductor Properties of > Electrical Properties
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