N.V. Joshi

New technique for analysing relaxation curves in photoconductors

Abstract The Fourier transform of the relaxation curves obtained in the photoconductivity process can be used to detect the existence of the delayed component and help to determine a few parameters of it uniquely. Using this method, a complete form of the relaxation curves (1024 data points) observed in single crystal of CdTe is successfully analysed for low intensity of radiation. A close agreement between experimental results and simulated values supports the proposed method of analysis.

Linear and sublinear photoresponse of CdS photodetector: A reevaluation

Abstract The rise and decay curves of a CdS photodetector were examined carefully for various radiation intensities. The obtained relaxation curves were precisely resolved into several components by using a recently developed technique and meaningful time constants were determined for different processes. This helped us to understand the origin for the linear, super- and sublinear behaviour of the photosignal on a realistic basis avoiding conventionally used ad hoc assumptions.

Local stability regions in dynamics of photoconductors

Abstract The stability analysis for the set of non-linear differential equations involved in the kinetics of the photoconductors has been carried out by examining the eigenvalues of the Jacobian matrix. We have assumed that the photoconductor is illuminated with high intensity radiation. It has been found that these eigenvalues critically depend upon the parameters of the traps and, for a certain set of values of the parameters, the system becomes unstable and reveals the possibility of chaos. We have determined the critical regions for different parameters where the system shows transitions from stable to unstable behavior.

DETECTIVITY OF THE PHOTOSENSORS: A REEVALUATION

Important parameters of the photosensors such as Noise Equivalent Power (NEP) and detectivity depend upon the magnitude of the signal to noise ratio. Recent improvements in the techniques of measurement in digitized form permit to process noise statistically with a suitable procedure and increase the detection capability more than expected from the conventional definition.

A new method to resolve transient photoresponse involving the sum of exponential terms

Abstract The analysis of a signal consisting of multi-exponential terms is a well known problem in examining the transient behaviour of photoresponse. Here, a method is proposed to analyze such signals with the help of the fast Fourier transform technique, which permits one to determine time constants uniquely with high accuracy. The method was verified for a commercially available CdS photodetector.

Study of the traps created in the single crystal of CdSe by the irradiation of Mo K α X-ray quantum

Abstract Traps were created in the single crystal of CdSe by bombardment with Mo Kα X-ray radiation. These traps were studied by the relaxation curves of photoconductivity, obtained at 6000 A and after two dosages of radiation. It has been found out that the traps created were β-type.