Nitride based semiconductor laser diode device with a bar mask

#This application claims the priority benefit of Taiwan application serial no. 91121531, filed on Sep. 20, 2002.

#1. Field of Invention

#The present invention relates to a semiconductor device by gallium nitride compound. More particularly, the present invention relates to a structure capable of applying on a gallium nitride laser diode device for increasing a thickness of a surface epitaxial layer. In the specification, the surface epitaxial layer is referring to a patterned epitaxial layer in the gallium nitride laser diode device.

#The accompanying drawings are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification. The drawings illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

#FIG. 1 is a cross-sectional view, schematically illustrating the structure of a conventional gallium nitride laser diode.

#FIG. 2 is a picture, schematically illustrating the crack occurring on the surface of the epitaxial layer for the conventional gallium nitride laser diode structure.

#Several terms used in the specification of the invention are generally described as follows. The term of gallium nitride compound semiconductor (GNCS) is referring to a form of AlxInyGa(1-x-y)N 0âXâ1, 0âYâ1, 0âX+Yâ1), which can be formed by, for example, metal organic chemical vapor deposition (MOCVD) or molecular beam epitaxial (MBE) crystal growth, or other similar epitaxial crystal growth. The dopants doped in the N-type gallium nitride compound semiconductor of the invention include Si, Ge, or other like elements with the same function. The dopants doped in the P-type gallium nitride compound semiconductor of the invention include Mg, Zn, Be, or other like elements with the same function.

#Embodiment 1: FIG. 3 is a cross-sectional view, schematically illustrating the structure of a gallium nitride laser diode, according to the first preferred embodiment of this invention. A substrate 301 is provided. The substrate 301 includes, for example, sapphire (Al2O3), silicon carbide (SiC), gallium nitride (GaN), Spinel (MgAl2O4), gallium arsenide (GaAs), zinc oxide (ZnO), silicon (Si), and so on. A gallium nitride compound semiconductor buffer layer 302 is formed on substrate 301 with an amorphous and/or polycrystallized structure and a thickness of 50 500 Angstrom. An N-type GNCS 303 is formed on the buffer layer 302 with a thickness of about 3 7 microns.

#After the crystal growth, the whole structure is shifted out from the crystal growing machine, and the coating, photolithography and etching processes are performed to form a lower bar mask substance 304 on the N-type GNCS layer 303. The direction of the bar can be any direction. The thickness can be, for example, 100 2000 Angstroms and the width can be, for example, 2 20 microns. The distance between the parallel bars in the bar mask substance 304 is about 2 500 microns. The bar mask substance 304 is used to cause multiple local crystal growing regions during the regrowth on the epitaxial layer, so as to change the distribution of strain force in the epitaxial layer and the growing direction of dislocation. As a result, the epitaxial layer formed over the N-type GNCS layer 303 has less dislocation density and strain energy. The bar mask substance 304 by itself has to have sufficient stability without producing the chemical reaction with the peripheral epitaxial materials, or contaminating the peripheral epitaxial materials. In addition, during the process of epitaxial growing, the epitaxy of GNCS does not directly grow on the mask substance. Each bar of the lower bar mask substance 304 has a cross-sectional shape in rectangular or any shape with similar functions. The mask substance 304 preferably includes silicon oxide, silicon nitride, or other material with similar function.