Laser Diode Structure & Materials

a summary of the basics of the laser diode structures and the materials used.

There may appear to be many similarities between a light emitting diode and a laser diode, the two are fundamentally different from an operational point of view. The laser diode is consists of heavily doped n+ and p+ regions. For manufacture it is normal to start with an n+ substrate and then the top layer can be grown onto this. The doping can be included in a variety of ways, either by diffusion, ion implantation or even deposited during the epitaxy process. A variety of materials can be used for laser diodes, although the most common starting substrates are Gallium Arsenide (GaAs) and Indium Phosphate (InP). These are known as type III-V compounds because of their places in the chemical periodic table of elements. Whatever material is used, it must be possible to heavily dope it as either a p type or n type semiconductor. This rules out most of the type II-VI materials, leaving the group III-V materials as the ideal option.

Apart from the basic semiconductor requirements, there are a number of optical requirements that are needed to enable the laser diode to operate. It needs an optical resonator. This must occur in the plane of the required light output. To achieve this the two walls of the laser diode that form the resonator must be almost perfectly smooth, forming a mirror surface from which the light can be reflected internally. One of the walls is made slightly less reflecting to enable the light to come out from the laser diode. Another requirement is that the two mirror surfaces must be perfectly perpendicular to the junction, otherwise the laser action does not occur satisfactorily. The two other surfaces perpendicular to the one of the required light output are roughened slightly to ensure that the laser action does not occur in this plane as well. In this way a resonant optical cavity is created. Although it is many wavelengths long it still acts as a resonant cavity.

By Ian Poole

<< Previous   |   Next >>

Share this page

Want more like this? Register for our newsletter

A medal for mobile medicine? Rudy Ramos | Mouser Electronics
A medal for mobile medicine?
Medical services the world over are coming under great pressure to deliver high-quality healthcare and, at the same time control costs. Alongside this, patients are becoming far more involved in their wellbeing as well as wanting a high standard of healthcare with even greater convenience than before. As people are more mobile these days, mobile healthcare (mHealth) avoids the need to visit the doctor’s office and allows patients to provide health data to providers, as well as receive care, anywhere on the planet.
Online - Designing GaN Power Amplifier MMICs
Learn how to design high performance GaN power amplifier MMICs

More training courses

Forthcoming Events

    . . . . More Events is operated and owned by Adrio Communications Ltd and edited by Ian Poole. All information is © Adrio Communications Ltd and may not be copied except for individual personal use. This includes copying material in whatever form into website pages. While every effort is made to ensure the accuracy of the information on, no liability is accepted for any consequences of using it. This site uses cookies. By using this site, these terms including the use of cookies are accepted. More explanation can be found in our Privacy Policy