Flicker-noise spectroscopy method

Authors: 
A. Mandziy, Z.A. Kolodiy, S.P. Yatsyshyn, A.Z. Kolodiy

Lviv Polytechnic National University

Method of determining the processes that take place inside the investigated system is presented here. Method is based on the analysis of energy spectrum of investigated system own noises. Using energy spectrum of own noises that is experimentally found it is calculated the constant of system relaxation time τ. Processes that take place inside the system affect the value of τ. Analysis of values of the constant of relaxation time gives the possibility to obtain the information about the character of inner processes.
Energy spectrum of own noises of real systems including semiconductors is not the same in the whole range of frequencies. On the middle and high frequencies energy spectrum value S(f) is the same  but on the low frequencies (f→0)  it  is observed the inverse proportion of spectrum from the frequency.
Such irregularity of energy spectrum is explained by unbalanced state of real system. Without external influences on the system (the condition of measurement) the system moves to balanced state through relaxation processes. Depending on the peculiarities of system structure defects the probability of one of all possible relaxation mechanisms with time τ is the highest. Analysis of times of relaxation spectrum gives the possibility to reveal almost all main characteristics of structure of solid solutions but empirical estimate of parameter τ is connected with some methodical difficulties and does not provide necessary precision of valuations. Energy spectrum of own noises of investigated system S(f) depends on the value τ thus the constant of system relaxation time can be found using experimentally calculated S(f). Value τ found in such way can be compared with theoretically calculated value τ during predicted the biggest probability the one of possible relaxation mechanisms. If experimental and theoretical τ value are close it is possible to find the relaxation mechanisms that take place in the investigated system.
The authors performed experimental investigations of energy spectrum of own noises of electronic elements based on resistors and also on silicon epitaxial planar diodes. In investigated resistors the relaxation processes are connected with appearing and disappearing of quasi-equilibrium vacancies. In semiconducting diode generating-recombination processes happen faster than appearing and disappearing of quasi-equilibrium vacancies, thus the relaxation constant for diode is smaller than for resistors. It was conducted the investigation of parameters of resistor own noises with conducted film of metal oxide on the surface and with mechanical damages of film. Based on the obtained energy spectrums of their noises it was calculated the relaxation constants of examples of investigated resistors.
In the structure of conducted film of investigated resistors besides quasi-equilibrium vacancies other defects appeared, for example micro-cracks. Appearing of such defects accelerate the relaxation processes that can be seen in the reduction of relaxation constants of investigated examples.