Karl Schuster

An experimental determination of the carrier lifetime in p-i-n diodes from the stored carrier charge

Abstract In a p - i - n diode carrying forward current, the increase of carriers in the weakly-doped middle zone depends upon the carrier lifetime τ. For the same forward current ( I Du ), the increase of carriers is higher the larger τ. The stored charge Q S in the middle zone is, therefore, a direct measure of the lifetime at ‘high-injection’. For a known geometry, the lifetime τ and the related carrier concentration n are determinable from two measureable quantities; the current I Du and the charge Q S . Experimentally, the stored charge can be extracted by a suddenly applied blocking impulse, and quantitatively determined if the duration of this procedure is so short that the loss due to recombination is negligible. This requirement is fulfilled by a suitably large blocking current ( I R ⪢ I Du ). Measurements upon alloyed p - i - n silicon rectifiers yield the so-called ‘high-level’ lifetime for different excess concentrations n . The agreement with other values of τ = f ( n ) obtained from H erlets characteristic curve analysis is very good.

Influence of the doping concentration on switching processes in psn rectifiers—II: Experiment

Abstract The evaluations of the temporal voltage development during the switching of a psn rectifier into the reverse state are confirmed by experiments on silicon rectifiers of p - and n -type material, having various doping concentrations in the middle region. For this purpose, the limiting case of a dominating doping influence is realized in all cases. In addition, the theory is clearly confirmed by probe measurements on cross-sectioned rectifiers.

Determination of the lifetime from the stored carrier charge in diffused psn rectifiers

Abstract The carrier lifetime in the middle zone of psn rectifiers ∗ at high injection can be determined by measuring a reverse current pulse. Formerly applied to alloyed rectifiers, this method was now also used with diffused rectifiers. Also in this case a good agreement was attained with the results of the evaluation of forward characteristics according to H erlet . At first, however, some difficulties arose concerning the determination of the thickness of the middle zone from the etched cross section as, besides the etching lines at the border of the lightly doped middle zone, also etching lines within the diffused regions became visible. The correct thickness could be finally found by using the impurity profile measured by four point probe method.

Switching processes in diffused rectifiers—II experiment

Abstract In a preceding paper the temporal development of the voltage during switching processes into the reverse state in diffused rectifiers with an exponential diffusionprofile was evaluated. In the present paper the evaluations are experimentally verified on silicon rectifiers, and for the technically interesting case of a doping concentration distribution typical of power rectifiers. Furthermore, the method is applied to the voltage increase in a rectifier having a more complicated diffusion profile. The result is experimentally verified.