GaAs based AlGaInP laser diode wafer can be supplied by PAM-XIAMEN with a band of 635nm. The III-V AlGaInP semiconductor material that can be lattice matched with the GaAs substrate has a wide direct band gap (1.9~2.3eV), a wide range of luminous wavelengths and high luminous efficiency. AlGaInP is the best material for preparing high-brightness red, orange, and yellow lasers and light-emitting diodes (LEDs). Following is a 635nm visible diode laser epi structure of GaInP / AlGaInP for reference:
1. Epi-structure of AlGaInP Laser Diode on GaAs Substrate
|Layer||Material||Mole Fraction (x)||Mole Fraction (y)||Strain (%)||PL (nm)||Layer Thickness (um)||Doping (E+18/cm3)||Type||Dopant|
2. Why Grow GaInP / AlGaInP LD Structure on Off-Angle GaAs Substrate?
The materials of GaInP / AlGaInP compressive strain confinement quantum well lasers are obtained by MOCVD one-time-epitaxial growth. The use of compressive strain in the active region can reduce the threshold current and operating current while improving the efficiency. Since GaInP and AlGaInP materials can easily form metastable ordered structures during the MOCVD epitaxy process, which should be avoided as much as possible in lasers, and disordered structures have narrower gain spectral line widths. In order to avoid the formation of ordered structure in the MOCVD growth of GalnP / AlGaInP materials, AlGaInP quantum well lasers generally use off-angle GaAs substrates. Moreover, the off-angle substrate can increase the p-type doping concentration in the confinement layer, thereby increasing the effective barrier of electrons in the active region, reducing the leakage of carriers, and helping to improve the high temperature performance of the device.
3. Why Grow MQWs of AlGaInP, Rather Than DH?
Compared with the DH (double heterojunction), the MQW (multiple quantum well) structure of AlGalnP can generate higher carrier density, thereby increasing the radioactive recombination efficiency; effectively shorten the length of the light-emitting region, thereby reducing the self-absorption of photons by the material. The GaInP / AlGaInP MQW produces quantum size effect, avoids the pollution of AlGaInP materials with high Al composition by oxygen, and effectively reduces the emission wavelength under low Al composition. Therefore, the AlGaInP laser diode array is grown with multiple quantum well structure instead of AlGaInP laser diode junction, widely used in optoelectronic devices, such as LD and LED, etc.
4. About Dopant of AlInP Layer in AlGaInP LD Epitaxial Structure
To solve the problems of carrier leakage, the AlInP with largest band is used as cladding layers. Due to the low refractive index, it can strongly restrict light conduction waves. And the AlInP layers need to highly dope with p-type or n-type, obtaining the electrical conductivity as high as possible. It is proofed that because of the lower diffusivity and better controllability, Mg is more suitable to be used as p-type dopant for AlInP than Zn. Meanwhile, it is found that adding undoped Mg barrier in Al(Ga) InP cladding layers can improve the emission efficiency of AlGaInP laser diode.
In terms of n -type doping of AlInP cladding layers, usually, Si is used as n type dopant for AlInP epi layers.