The method uses the photoelectric sensitivity of the diode junctions. It consists, in order to test a specific diode belonging to a group of diodes connected in parallel, in illuminating the junction of a diode in question with light belonging to the range of photoelectric sensitivity of the said junction, in connecting the group of diodes to the terminals of an electrical load and in noting the appearance, at the terminals of the said load, of a photocurrent denoting correct operation of the diode in question. When the group of diodes forms part of an assembly within which it is connected in series with other groups of diodes, the diode under test is illuminated by intermittent light while at least one diode of each of the other groups is illuminated continuously and while an attempt is made to detect an intermittent photocurrent passing through a load to the terminals of which the assembly is connected. In the figure can be seen a test device which comprises an array (1) of electroluminescent diodes and a photocurrent detector (2) which are driven by a computer (3).

A defect detection of light-emitting diodes (LEDs) is electrically performed on a large-scale display, comprising a plurality of light-emitting diodes arranged by a predetermined arrangement on an image display face, voltage detection portions for applying a constant current to a plurality of light-emitting diodes in an off region at a forward voltage or less in accordance with an input of a signal indicating a defect detection mode and detecting voltages between terminals of light-emitting diodes arising when the constant current flows there through, and a defect detection portion for electrically detecting a defect from the plurality of light-emitting diodes based on detection results of the voltage detection portion; and drive circuit devices (driver ICs) having the above configuration are serially connected and an electric signal indicating a result of defect detection is output from its final stage.

A method of testing a semiconductor device, having the steps of pulsing the semiconductor device with a predetermined level of current for a duration of time so as to cause inadequate parts to degrade and to cause adequate parts to stabilize, and measuring predetermined electrical or optical performance characteristics for the semiconductor device after the current pulse. A system for testing a semiconductor device on a wafer is also provided having a contact probe for applying current pulses to the semiconductor device on the wafer, measuring means electrically connected to the probe for measuring predetermined electrical or optical performance characteristics of the semiconductor device on the wafer, and optical detection means electrically connected to the measuring means for detecting radiation emitted from the semiconductor device on the wafer.