A. Russell Schaefer

Complete collection of minority carriers from the inversion layer in induced junction diodes

Mechanisms limiting the internal quantum efficiency in various types of oxide‐passivated silicon photodiodes are discussed. It is argued that unit internal quantum efficiency is achievable in metallurgical junction, oxide‐n+‐p‐p+ photodiodes, if it is achievable in the inversion layer of induced junction diodes of the same type. Measurements of the variation in response of the latter type of photodiode under both oxide bias and reverse bias are described. The results indicate that 100% collection of the minority carriers generated in the inversion layer is achieved for sufficiently low flux levels. Implantation in the oxide of Na+ ions to augment the trapped positive charge increases the maximum flux level at which 100% collection is observed.

Reflectance and external quantum efficiency change of a silicon photodiode after surface cleaning

During the process of remeasuring the external quantum efficiency (spectral response) of some previously calibrated NBS silicon photodiodes, evidence was seen of a change in their reflectance. This is an important change in detectors that are to be used for radiometric measurements, so there is a continuing investigation into possible causes for such effects. One such cause that was considered was the slow formation of an impurity film on the detector surface as a function of time. The type of detector used in the NBS calibration program has a silicon dioxide antireflection coating. (This detector is described in more detail elsewhere.) It was believed that the formation of such a film could appreciably alter the reflectance of the SiO2 coating, causing, for example, an increase in reflectance with an attendant decrease in external quantum efficiency. To test the validity of the above hypothesis, one detector of the type just described was selected. This detector and the ones used in the calibration program have been exposed to the same atmospheric conditions (those of our laboratory) for several years. The detector was placed in a referenced holder so that two different positions, A and B in Fig. 1, on its surface could be repeatably accessed. Using a 632.8-nm beam of approximately 1 mW from an He–Ne laser, we measured the reflectance and external quantum efficiency of these two positions on each side of the detector five times and averaged the results. The external quantum efficiency was obtained from a measurement of the power in the He–Ne beam using an electrically calibrated dc thermopile radiometer, and the reflectance, almost all of which was specular, was measured using another silicon detector to intercept the reflected beam from the detector being tested. These techniques have been detailed elsewhere. After these measurements were made, the half of the detector indicated in Fig. 1 was cleaned using high-purity (spectral-grade) methanol in the same manner as one would use to clean laser optics. The other half was left uncleaned to serve as a control reference in the experiment. After the cleaning, the detector was repositioned, and both spots A and

Measurement of Geometrically Total Spectral Radiant Power

In this paper, the measurement of geometrically total spectral radiant power, i.e., the spectral radiant power emanating in all directions from a light source, is discussed. A gonioradiometer employing a silicon photodiode and a set of narrow band interference filters was used for these measurements. The experiment is described, some exploratory measurements are presented, and the uncertainties which this method introduces are estimated.