Optimization of Laser Bar Orientation for Nonpolar Laser Diodes

Brief Description

A method for the growth and fabrication of nonpolar laser diodes. 

Background

Growing nitride laser diodes along the polar c-direction causes a polarization-induced electric field that causes a large effective hold mass that is detrimental to performance. Alternatively, growing nitride thin films along a nonpolar axis offers a means of eliminating polarization effects and reducing the effective hole mass in device structures. These changes should help to decrease the current densities necessary to generate optical gain in nitride laser diodes. In particular, nonpolar nitride laser bars should be properly oriented with regards to the planes of semiconductor crystals in order to achieve the aforementioned benefits.  

Description

Researchers at UC Santa Barbara have developed a method for the growth and fabrication of nonpolar laser diodes. The structures can be grown either directly on free-standing nonpolar substrates or on nonpolar template layers pre-deposited on a foreign substrate. Many growth techniques are suitable for the method, including metalorganic chemical vapor deposition (MOCVD), hydride vapor phase epitaxy (HVPE), and molecular beam epitaxy (MBE). For m-plane nitride laser diodes, optical gain is maximized when laser bars are oriented along the c-axis and minimized for laser bars oriented along the a-axis; for a-plane devices, optical gain is maximized for laser bars oriented along the c-axis and minimized when oriented along the m-axis. This in-plane, orientation-dependent gain is a phenomenon that is currently unique to nonpolar nitride laser diodes. 

Advantages

·         Superior manufacturability of nitride laser diodes

·         Improved device performance through elimination of polarization-induced electric fields and reduction of effective hole mass

·         Decreased current densities necessary to generate optical gain

·         Less heat generation, longer device lifetimes, and higher production yields

Applications

·         Solid-state lighting systems, including projection displays

·         High-resolution printers

·         High-density optical data storage systems

·         Optical sensing

Patent Status