Determination of Energy Gaps for Some Semiconductors Devices

Abstract

In this work two light emitting diodes, two ordinary diodes, two light dependent resistors, beside two transistors are connected to a simple electric circuit. This circuit consists of a power supply, ammeter and voltmeter. Fifty (50) readings for voltage(mV) and current(mA) are taken. A graph relating the current to the voltage is drawn for only one sample from each semiconductor type . It was found that for light emitting diode the current increases abruptly at about 0.2 Volt, while for the ordinary diode the change is at about 0.2 Volt. For light dependent resistor the change is about 0.2 Volt, where as it changes abruptly at about 0.4 Volt for transistors. These may indicate the existence of energy gas. The value of the corresponding gaps are less than the ordinary values, which may result from heavy doping. The values of gaps indicates that the impurities are Cu and Fe. The exposure of these sample to the heat increases the current which agrees with the fact that heat increases electron velocity. The exposure of samples to the magnetic field broadens the energy gap which agrees with some works.