We all know that blue laser diodes are widely used in daily life. Many people ask what they mainly rely on to emit light. What is the main light-emitting structure? Let's take a look at it.

Blue laser diode is generally based on gallium nitride (GaN) material system, which is what we often call GaN semiconductor. Its core structure is actually divided into several layers, from bottom to top: substrate layer, N-type layer, quantum well layer and P-type layer. Together, these layers are like a "sandwich biscuit", and the secret of luminescence is hidden in the quantum well in the middle layer.

Let's start with the bottom.

Blue laser diodes are usually made of sapphire (Al₂O₃) or SiC or GaN substrates. The function of this substrate is to provide a "foundation" for the whole crystal growth, so that the materials behind it can grow neatly and have fewer defects. The choice of substrate will affect the quality of crystal and indirectly affect the efficiency and life of light. At present, the high-end blue laser generally uses GaN self-supporting substrate, which has more stable performance and higher cost.

Further up is the N-type GaN layer, which is mainly used for conducting electricity. By doping silicon (Si), a region with high electron concentration is formed to ensure that electrons can run smoothly to the light-emitting region.

On the top, there is a P-type GaN layer, which is doped with magnesium (Mg) to provide holes (that is, the "counterpart" of electrons). When you are energized, electrons run from the N-type region to the P-type region, and holes move in the opposite direction. They meet and recombine in the MQW structure in the middle layer, and photons are generated, which is the laser we see.

Then why is it called a quantum well?

Simply understood, electrons and holes are locked in a very thin area, making them "easier to meet". This structure can greatly improve the recombination efficiency and make the luminescence wavelength more stable.

Another key point is the optical waveguide structure.

In order to realize stimulated emission and form resonance, laser must have an optical cavity. Blue laser diodes generally form a high reflection and a low reflection at both ends. When photons reflect back and forth in the cavity, they are constantly amplified and finally output from the low negative side to form laser. This structure is like an extremely narrow channel, where the light is trapped and forced to become very concentrated, so the brightness and energy density are several orders of magnitude higher than those of ordinary LEDs.

The above is the structure of blue laser diode. If you still don't understand, you can contact us at any time.