Publisher Summary This chapter highlights noise as a measure of quality and reliability in electronic devices The chapter attempts to describe what mechanisms have been well established as a source of noise related to the defective or nonideal nature of electronic devices This chapter is devoted to an account of the success that has been obtained in using noise as a nondestructive indicator of reliability The chapter is mainly concerned with a review of the properties of noise and some of the general principles behind the specific mechanisms Noise arises from many possible defects so that monitoring this single quantity can detect the presence of one or more of many different defects It is, therefore, necessary to be careful in interpreting noise results to ensure that a correct mechanism is assigned to the noise, and even greater care is necessary in comparing noise results among different specimens, because the origins and characteristics of the noises may be completely different As many of the detailed mechanisms for the production of the excess noise are becoming understood, the use of noise as an analysis quantity can increase

Electrical Noise as a Measure of Quality and Reliability in Electronic Devices

The model of electroluminescence in forward-biased MS and MIS light-emitting diodes based on the Auger recombination on the contact surface of the semiconductor is developed. Such a model may provide a light emission with the threshold voltage Uth = (Eg/2e) – (Efs/2e) < hνmax/e or even Uth = (hνmax/2e) – (Efs/e), depending on the physical processes involved. Here Eg, is the energy gap of the semiconductor, Efs the Fermi energy level in the semiconductor with respect to the c-band edge, hνmax the maximum of the electroluminescence band, e the electron charge. Experimental results obtained on ZnS MS and MIS diodes essential for this model are presented and analysed. It is found that the spectral distribution of diode emission remains practically unchanged at biases close to the threshold voltage Uth. The conclusion is drawn that the electroluminescence and the forward current have typical tunnel characteristics even in the case of ZnS MIS diodes with i-layers several thousand angstroms thick. The main physical properties of zinc chalcogenide light-emitting diodes are explained by means of the model developed.



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Mechanism of electroluminescence excitation in forward‐biased MS and MIS light‐emitting diodes based on wide‐band‐gap II–VI compounds

Low frequency noise as a tool to study optocouplers with phototransistors

The current-voltage (I-V) characteristics and low-frequency noise of the GaN p-i-n diodes were investigated in temperature range from 10 K to 300 K. We found that the reverse biased p-i-n diode made of GaN/AlGaN exhibits features of the space charge limited (SCL) current flow and its I-V characteristics can be approximated by the power law I~Vn relation. This phenomenon can be attributed to the presence of the multiple charge traps in the intrinsic region of device. It has been demonstrated that the direct tunneling from traps to bands may occur in diodes at forward and reverse bias with strong support of the Frenkel effect. The low frequency noise in our devices does not depend on temperature in both bias directions under cryogenic conditions. The observed low-frequency noise features support the hypothesis that excess tunneling current and recombination at grain boundaries are origins of the 1/f low-frequency noise in the diode at forward bias. The 1/f noise in the reverse bias regime can be described as a composition of many Lorentzian noise components that originate from traps, which have specific depth distribution

On Charge Transport and Low-Frequency Noise in the GaN p-i-n Diode

Light and voltage noise in AlxGa1–xAs–GaAs heterolasers are studied in a wide range of forward currents (i = 10−7 to 4 A) and frequencies (f = 1 to 107 Hz). The noise characteristics obtained are compared with those observed on GaAs laser diodes. Results of investigations carried out on samples of both types are similar. Components of 1/f-type are found in the spectra of light noise as well as in the spectra of voltage noise. At currents below the threshold value, these components are correlated with each other and are due to the fluctuations of the nonradiative component of the diode current. The reasons for the changes in the 1/f-noise which take place at the sample change-over to the laser action are discussed. As the change-over to the laser action occurs, the sharp increase of frequency-independent high-frequency light and voltage noise predicted by the theory is found experimentally. These noises appear to be fully correlated with each other, the phase shift between the fluctuations of light and of voltage on the diode contacts being equal to 180°. In addition, the change of the noise characteristics taking place in the course of diode operation is disclosed and analysed. As a result a connection is established between the processes of the slow laser degradation and the peculiarities of the excess component of the diode current as well as of its low-frequency noise.



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Light and voltage noise of lasers based on AlxGa1–xAsGaAs heterojunctions

The excess fluctuations of the direct current and of the forward-bias electroluminescence intensity in GaAs-diodes have been investigated. The diodes of two types have been studied: the samples doped by non-amphoteric impurities (type I diodes) and the samples doped by non-amphoteric together with amphoteric impurities (type II diodes). The current noise in type I samples as well as in the wide current range in type II samples is shown to be generated in the space charge region of diodes. These noises are as a matter of fact the fluctuations of the excess component of the whole current which is likely to pass through some ‘peculiar’ regions of p - n -junctions rather than through the whole area. The current noise observed in type II diodes at sufficiently large currents is due to the fluctuations of the resistance of the compensation region of the diode or due to the fluctuations of its contact resistance. The excess electroluminescence noise in all diodes investigated has been found to be connected with the above-mentioned fluctuations of the excess component of the whole current and in the type II samples the over-barrier electron flow responsible for the electroluminescence passing probably through the same ‘peculiar’ regions of p - n -junction as the excess current does.

M.N. Zargarjantz

Papers

Nature of current and of forward-bias electroluminescence excess noise in GaAs-diodes