Basic LED Materials
An LED is a light emitting diode that rests on a semiconductor material (aluminum gallium arsenide). The LED bulb has no filament, so it won't burn out like an incandescent light bulb. The semiconductor is typically not a very good conductor of electricity because the material (aluminum gallium arsenide) is composed of atoms which line up flawlessly, leaving no free electrons for which to convey electricity. Electrical current is allowed to pass through the LED's semiconductor medium by coating the circuit of the semiconductor with both a positively charged material and a negatively charged material.
Electron Flow
The electrical current in an LED flows in one direction when turned on, and reverses direction when turned off. When voltage is not applied the electrons move from the negatively charged material to the holes (on the atomic level) in the positively charged material, filling in the holes of the positive material. This action forms an insulating state in the material, thus no electricity is allowed to flow (no gaps for free electrons to move through). When the LED diode is turned on to light a monitor, for example, an electrode with a negative current is applied to the negative material of the semiconductor. The two negative charges repel each other, thus sending negative particles (electrons) away from the electrode. A positive electrode is applied to the positive material of the semiconductor, and in effect pushes the positive particles out of the material. The positive particles move toward the negative electrode, while the negative particles move toward the positive electrode. Carrying the current is a cathode lead (-) and an anode lead (+) running from the diode to the battery.
Produce the Desired Light Frequency
The "Depletion Zone" rests as a junction between the positive/ negative sides of the semiconductor. When the voltage is turned off, the junction becomes an insulating material (no gaps for electrons to move across). Apply more current to the circuit, and the junction sends its electrons into higher frequencies. Some electrons fall through the gaps in the material as they move from a higher level to a lower level of orbit. These "falling" electrons produce photons (particles without mass, but with high momentum and energy). The photons produce varying frequencies of light in the junction between the positive and negative materials. The key to producing the desired frequency of light is the material which the diode is constructed from. To make a remote control LED for a television, use a silicon diode to produce infrared light. The distance the electron falls from higher to lower orbit is short, thus producing low frequency infrared light. If you want to light a digital face (such as a clock or microwave indicator), purchase a diode with wide gaps in the material. Wide gaps allow electrons to fall farther, producing higher frequency/visible light.
Tags: charged material, electrons move, aluminum gallium, aluminum gallium arsenide, between positive, between positive negative, direction when