Infrared absorption spectrum of neutral magnesium donors in silicon

The infrared absorption spectrum of neutral magnesium donor impurities in silicon has been investigated under the high resolution of a Fourier-transform infrared spectrometer. The absorption spectrum measured at liquid helium temperature are observed to be clearly better than those reported earlier in the literature. Several new lines corresponding to excitation from ground state to higher excited states have been observed and identified.     

Infrared absorption spectrum of singly ionized magnesium donors in silicon

The infrared absorption spectrum of singly ionized magnesium donor impurities in silicon has been measured. Due to better sample preparation and higher resolution of the instrument, the absorption spectrum obtained is much better than previous reports. Some new lines have been observed and identified. Besides the 2p_± line, the 3p_± line has also been observed for the first time to be a doublet indicating that the excited state np_± splits into two states due to chemical splitting.     

Terahertz absorption and emission upon the photoionization of acceptors in uniaxially stressed silicon

Experimental data on the spontaneous emission and absorption modulation in boron-doped silicon under CO₂ laser excitation depending on the uniaxial stress applied along the [001] and [011] crystallographic directions are presented. Room-temperature radiation is used as the probe radiation. Low stress (less than 0.5 kbar) is shown to reduce losses in the terahertz region by 20%. The main contribution to absorption modulation at zero and low stress is made by A⁺ centers. Intersubband free hole transitions additionally contribute to terahertz absorption at higher stress. These contributions can be minimized by compensation.     

Thermal acceptors in irradiated silicon

Comparative analysis of the conditions for the formation of shallow acceptor centers upon high-temperature annealing in silicon irradiated with electrons, neutrons, and energetic ions is performed. The introduction of a sufficiently large (in comparison with the initial concentration of impurities and defects) concentration of radiation-induced distortions of the silicon lattice is shown to lead to the formation of thermal acceptors stable up to annealing temperature of ～650°C. The acceptor formation is supposed to be due to the interaction of background acceptor impurities (supposedly boron) with vacancies “stored” in multivacancy clusters and released upon their breakup.     

Free carrier absorption in silicon

Free carrier absorption in heavily doped layers reduces the useful photon flux in the photoconductive region of extrinsic Si infrared detectors. A simple theory is developed which predicts the transmissivity of such layers as a function of their sheet resistance and the wavelength of the radiation. Experimental data over the 2.5-20 µm wavelength and 5-500 Ω/square sheet resistance range are given for both diffused and ion-implanted layers and also for polysilicon gases. The temperature dependence of both transmissivity and sheet resistance is investigated from 20 to 300 K.     

Infrared absorption behavior in CdZnTe substrates

Infrared (IR) optical transmission measurements of polished CdZnTe wafers can provide useful information about excess impurities, stoichiometry, and inhomogeneities (precipitates and inclusions). We have investigated the IR transmission behavior of Cd_0.96Zn_0.04Te between 8 m and 20 m at room temperature. The measurements were made before and after thermal treatments involving control of the Cd and Zn overpressures, which served to minimize the Cd (cation) vacancy population. Our results support the polar optical phonon scattering theory of Jensen, according to which the absorption in donor dominated CdZnTe varies as^m with m=3. For material dominated by acceptors, we show that the theoretical absorption by inter-valence band transitions can be approximated by a similar power law with exponent m=1, and that Cd-vacancy dominated wafers are in reasonable agreement with this. We find some wafers in which the asgrown condition exhibits partial compensation of impurity donors by Cd vacancy acceptors, and demonstrate removal of the compensation by annealing to fill the vacancies. In a separate group of wafers, we find that an observed increase in absorption occurring during growth of a HgCdTe layer by liquid phase epitaxy can be explained in terms of an increase in Cd vacancies caused by diffusion of Cd to Te precipitates. This effect can be reversed by annealing in Cd−Zn vapor, which fills vacancies and eliminates some precipitates. Impurity concentrations were measured by glow discharge mass spectrometry (GDMS).     

Infrared spectroscopy of bonded silicon wafers

Infrared spectra of multiple frustrated total internal reflection and transmission for silicon wafers obtained by direct bonding in a wide temperature range (200–1100°C) are studied. Properties of the silicon oxide layer buried at the interface are investigated in relation to the annealing temperature. It is shown that the thickness of the SiO₂ layer increases from 4.5 to 6.0 nm as the annealing temperature is increased. An analysis of the optical-phonon frequencies showed that stresses in the SiO₂ relax as the annealing temperature is increased. A variation in the character of chemical bonds at the interface between silicon wafers bonded at a relatively low temperature (20–400°C) is studied in relation to the chemical treatment of the wafers’ surface prior to bonding. Models of the process of low-temperature bonding after various treatments for chemical activation of the surface are suggested.     

Infrared laser heterodyne ozone spectrum

An infrared laser heterodyne spectrometer (IRLHS) has been developped for both laboratory and atmospheric studies. A long path and temperature adjustable cell has been designed for laboratory spectra. An ozone spectrum with 5MHz (0.00016 cm^?1) resolution is presented.     

Optical absorption of gallium-doped silicon

The spectral dependence of the infrared absorption of Ga centers in silicon has been measured. Dependence on doping and impurity concentration and temperature is found for the optical cross section. The splitoff valence band has to be taken into account to explain the spectral dependence. Excited bound states cause a temperature decrease of the optical cross section.     

Unusual absorption “band” in the infrared spectrum of silicon annealed at high temperature and then rapidly cooled

An unusual absorption “band” with a giant half-width has been detected in the infrared absorption spectra of silicon obtained by zone melting and subjected to cyclic heat treatment at 1250 °C with rapid cooling after each anneal and with partial removal of the thermal oxide in each cycle. A model explaining the observed features of the spectrum in terms of the transformation, occurring during heat treatment of impurity nanoprecipitates contained in the initial silicon and in terms of the microblock structure of the material is proposed. Fiz. Tekh. Poluprovodn. 31, 247–249 (February 1997)     

磷酸盐激光玻璃中水的红外吸收

本文测量了若干种磷酸盐激光玻璃的红外吸收光谱,得3.5、4.25、6.0μm三个较强的吸收峰.探讨了它们产生的原因;同时研究了碱金属氧化物和氧化铝含量对吸收峰的影响;水份对玻璃密度和机械强度的影响.     

Infrared photoconductivity via deep copper acceptors insilicon-doped, copper-compensated gallium arsenide photoconductiveswitches

Silicon-doped, copper-compensated, semi-insulated gallium arsenide of various doping parameters was studied with respect to infrared photoconductivity. This material is used as a photoconductive switch, the bistable optically controlled semiconductor switch (BOSS). One limitation was the relatively low conductivity of the device during the on-state. Typically, silicon-doped gallium arsenide is converted to semi-insulating gallium arsenide by the thermal diffusion of copper into the GaAs:Si. It is shown that variation of the diffusion parameters can improve the on-state conductivity by the enhancement of the concentration of a copper center known as Cu_B. The conductivity of the device 150 ns after irradiation from a 20-ns FWHM laser pulse (λ=1.1 μm) is recorded for various incident energies. This on-state conductivity saturates at a value that is predicted by the densities of the copper levels and the mobility     

Infrared reflectance and absorption of N-type InP

It has been shown that measurement of the infrared reflectance minimum frequency offers a simple, non-destructive method to determine carrier densities of n-type InP. Free carrier absorption has been measured for InP with carrier densities of 0.4-9 × l0¹⁸/cm³ in the spectral range of 1.1-l0μm and discussed in terms of optical phonon scattering and impurity scattering. In particular, the absorption at λ= 1.3μm should be considered in the design of long wavelength photodetectors and light emitting diodes to improve external quantum efficiencies.     

Infrared and submillimeter spectroscopy of grooved silicon structures

Transmission of grooved silicon structures with 4-and 7-μm periods is studied by polarization-sensitive IR and submillimeter spectroscopy in a wide spectral range. The experimental results obtained in the range 1–10-μm are explained in terms of geometrical optics taking into account the scattering of radiation. In the far-IR (20–2000 μm) range, the structures exhibit a strong birefringence, which can be described in terms of the effective medium model in the electrostatic approximation. An influence of photoexcitation on the optical transmission and its anisotropy is observed; this effect can be explained in terms of the effective medium model taking into account the interaction of radiation with free carriers.     

Light absorption and photoluminescence of porous silicon

The results of an experimental study of Raman scattering, photoluminescence, and light absorption and reflection in porous silicon layers obtained by electrochemical etching of single-crystal wafers are presented. It is concluded on the basis of an analysis of the experimental data that the centers responsible for radiative and nonradiative recombination in this material are of a multiple character. The experimental data show that the centers whose maximum of optical excitation lies in the blue-green region of the spectrum have a uniform distribution, in contrast with the centers whose region of efficient excitation lies in the red region of the spectrum. The radiative recombination efficiency of the latter increases in a thin, near-surface layer of a porous-silicon film. Fiz. Tekh. Poluprovodn. 32, 1001–1005 (August 1998)     

表面等离子体增强硅电池光吸收的研究进展

局域表面等离子体共振(LSPR)是光照射金属纳米粒子而引起金属内的自由电子发生集体共振使粒子周围的近场增强。将LSPR应用于太阳能电池,会使陷光效率大大增加,而同时降低表面复合损耗和电池基底的厚度要求。文章从粒子的大小、形状、阵列模式的周期及粒子周围的介电环境对太阳能电池的陷光的影响,介绍了基于LSPR性质的表面等离子体硅太阳能电池的陷光机理及其影响因素,对相应的研究做了系统的综述。     

多孔硅吸收光谱和反射光谱

测定了多孔硅的吸收光谱和反射光谱，结果发现其吸收边对应于可见光区域。同单昌硅要比，其吸收边发生了蓝移，并且吸收强烈。由多孔硅反射谱曲一，利用Ｋ－Ｋ关系对其光学常数进行了简单的计算和分析。     

Energy spectrum of acceptors in the semimagnetic semiconductors p-Hg1−x MnxTe in the spin-glass region

The far-IR transmission and photoconductivity in the semimagnetic alloys p-Hg_1−x Mn_xTe (x=0.20–0.22) at temperatures 2–7 K were investigated at fixed frequencies of optically pumped molecular lasers in the region 49–311 μm. We report the observation of photoexcitation of acceptors from the ground into excited states under conditions when the direct interaction of the magnetic moments of the manganese ions becomes substantial and results in the formation of a spin-glass phase. It was found that the internal field produced by the spontaneous and external polarizations of the magnetic moments of the Mn²⁺ ions in the spin-glass temperature range influences the energy spectrum of acceptors in a magnetic field. Fiz. Tekh. Poluprovodn. 32, 450–452 (April 1998)