V. A. Kozlov

Doping of semiconductors using radiation defects produced by irradiation with protons and alpha particles

One of the modern methods for modifying semiconductors using beams of protons and alpha particles is analyzed; this modification is accomplished by the controlled introduction of radiation defects into the semiconductor. It is shown that doping semiconductors with radiation defects produced by irradiation with light ions opens up fresh opportunities for controlling the properties of semiconducting materials and for the development of new devices designed for optoelectronics, microelectronics, and nanoelectronics based on these materials; these devices differ favorably from those obtained by conventional doping methods, i.e., by diffusion, epitaxy, and ion implantation.

Impact ionization wave breakdown of drift step recovery diodes

High frequency IMPATT oscillations followed under certain conditions by reversible impact ionization wave breakdown of the p+-n-n+ diode structure have been experimentally observed for the first time in a drift step recovery diode operating in the avalanche breakdown mode after a fast voltage restoration of the p-n junction.

Laser thermowave diagnostics of heat transfer through bonded interfaces in multielement semiconductor opening switches

Laser thermowave photodeflection methods have been used to study the process of heat transfer in bonded interfaces of semiconductor diode structures of high-voltage opening switches fabricated according to the stack technology. A theoretical model is proposed for the description of thermal wave propagation in these structures with allowance for technological features of the preparation of semiconductor surfaces, brazing layers, and welds. It is shown that laser thermowave photodeflection methods can be used for diagnostics of the quality of bonded interfaces between elements of high-voltage opening switches fabricated by means of various technologies.

Defect engineering for carrier lifetime control in high voltage GaAs power diodes

The paper considers the physical basis for the technique of controllable defect formation at heterointerfaces and in the bulk of epitaxial GaAs layers in the process of isovalent doping. Results of studying crystal defects and their rearrangement depending on the isovalent doping modes in the process of epitaxial growth are presented. The main aspects of the defect influence on the charge carrier lifetime as well as on the diode structure blocking voltage are analyzed. Particular cases of the developed technique application for controllable defect formation in fabricating such GaAs-based devices as Hyper Fast Recovery Epitaxial Diodes and Drift Step Recovery Diodes are considered.

Study of the potential distribution in a forward-biased silicon diode using electrostatic force microscopy

Electrostatic force microscopy was used to study the potential distribution in a forward-biased epitaxial-diffused n+-n-p-p+ silicon diode. Distributions of potential and capacitance were determined across the cleaved surface, which intersected the layers in the diode structure. Variations in the surface potential and capacitance were preliminarily measured with a submicrometer spatial resolution and were used to determine the position and width of the n-p junction; the distribution of applied forward bias in the diode was also assessed. It is shown that an additional potential barrier for injected charge carriers may exist in the vicinity of the n+-n junction in the diode under consideration. For an injection-current density exceeding 100 mA/cm2, the voltage drop across this barrier becomes comparable with the voltage variations across the operating n-p junction.

Detection of paramagnetic recombination centers in proton-irradiated silicon

The method of spin-dependent recombination was used to record electron spin resonance (ESR) spectra of recombination centers in a thin (∼1 µm) surface layer of p-type silicon grown by the Czochralski method and irradiated by protons with energies of ∼100 keV. Spectra of excited triplet states of the oxygen + vacancy complex (A-centers) were observed along with complexes consisting of two carbon atoms and an interstitial silicon atom (CS-SiI-CS complexes). The intensity of the ESR spectra of these radiation-induced defects was found to be largest at irradiation doses of ∼1013 cm−2, and decreased with increasing dose, which is probably attributable to passivation of the radiation-induced defects by hydrogen.

Transport of charge carriers through the thin base of a heterobipolar transistor under the impact of radiation

The transport of electrons in heterobipolar transistors with radiation defects is studied under conditions where the characteristic sizes of defect clusters and the distances between them can be comparable or can even exceed the sizes of the device base. It is shown that, under some levels of irradiation, neutron radiation can bring about a decrease in the time of flight of hot electrons through the base, which retards the degradation of the transistor parameters.

Estimation of quality of GaAs substrates used for constructing semiconductor power devices

X-ray topography and high-resolution diffractometry methods are used for testing GaAs wafers from different manufacturers, which are used as substrates for epitaxial growth in construction of power semiconductor devices. Typical features of such wafers are a distorted surface layer, bent, and growth dislocations with two types of distribution with a density of (1–2) × 104 cm−2. The best and worse substrates are determined from the finishing of the working surface, and the optimal combination of X-ray methods for estimating the quality of finishing of the working surface of the crystals with a high level of X-ray absorption is established.

Impact-Ionization Wave Breakdown and Generation of Picosecond Pulses in the Ultrahigh-Frequency Band in GaAs Drift Step-Recovery Diodes

It is shown experimentally for the first time that the operation of GaAs drift step-recovery diodes produced on the basis of p+-p0-n0-n+ is accompanied by the generation of ultrahigh-frequency oscillations in the form of trains of short pulses with a duration of ∼10 ps. The amplitude and repetition frequency of these pulses are as high as ∼100 V and ∼(10–100) GHz, respectively. The phenomena of delayed reversible wave breakdown and excitation of ultrahigh-frequency oscillations in the structures of GaAs step-recovery diodes are found to open up new avenues for progress both in the physics and technology of semiconductor devices based on GaAs structures and in the technology of ultrahigh-frequency systems and devices that deal with pulsed signals of picosecond-scale duration.

Use of direct wafer bonding of silicon for fabricating solar cell structures with vertical p-n junctions

A technology based on ion implantation and the direct wafer bonding of p+-p-n+ structures has been developed for multijunction silicon solar cells. The internal quantum efficiency of such structures is close to unity in the wavelength range 350–900 nm.