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Acoustic emission express-method of control reliability of semiconductors light-emitting structures

№ 17 The department  for problems of defect formation and nonequilibrium processes in complex semiconductors
    A.I. Vlasenko, O.V. Lyashenko, V.P. Veleschuk

Light-emitting diode on acoustoelectric sensors (a) and acoustic emission signal with a quantum yield oscillation (b).

Purpose - for use in areas of the industry
    The given method is passive ultrasonic nondestructive express-method which allows revealing in a real time mode in semiconductor light-emitting structures the beginning fast degradation processes at passage a constant direct current.

 Principle of action.
    The method allows, unlike overwhelming majority of other quality monitoring of semiconductor materials, structures and devices, in a real time mode without damage of the investigated sample, to fix in light-emitting structures and devices the beginning of process of intensive degradation due to formation structural defects or intensive processes of change of their energy condition at current passage.
    The principle of action of development is based on the phenomenon of acoustic emission (АE) which means radiation of internal spontaneous acoustic wave’s noise character at local dynamic reorganization of solid state structure which is accompanied by formation and failure of mechanical pressures in local volumes at action of external fields of the different physical nature.
    The offered method allows in light-emitting structures and devices testing to define their individual maximal-achievable or authentically increased parameters of their use, in particular - to define a current which corresponds the beginning of processes active defects formation, i.e. a AE occurrence threshold and the maximal density of a current before actually destruction.
 The features of development are following:
•    The current density of J_і with simultaneous AE registration through a light-emitting diode increases at a walk, i.e. in everyone following(i+1)-th increase (step) value of current density through a light-emitting diode makes J_і+1= (2...1,5)·J_і. At everyone J_і AE registered to operation of all potentially active (for given J_і) AE sources, i.e. to AE discontinuance.
•    At technological quality assurance (on CVC measurements) structures on the common lining enough unitary fastening (acoustic contact to lining).
•     Offered method is completely compatible for simultaneous use to the majority of other quality monitoring of semiconductor materials, structures and devices, in particular - measurement of electroluminescence spectra, CVC, etc. The received information is partially complementary.
    The scope of the offered development can be expanded on other external influences, materials, structures and devices.

The basic technical and economic characteristics of development
    Registration of AE signals to be carried out acoustoelectric sensors from the complete set dualchannel acousticemission device AF-15 which in strips of frequencies 20-200 кHz, 200-500 кHz and 500-1000 кHz have approximately identical relative sensitivity in the middle of a corresponding strip.
    Amplification (on 78...85 dB) and the previous processing of electric AE signals can be carried out AF-15 or by means of the similar device. The further processing and registration is carried out by a computer by means of the corresponding software.
    There is an opportunity of full automation of control process.
    The estimated cost of development, depending on the form of realization, makes from 10 000 up to 60 000 USD.