PAM-XIAMEN Offers GaAs LED epitaxy wafer, which is AlGaInP LED (Red LED) stack on GaAs substrate. Xiamen Powerway Advanced Material Co.,Ltd., a leading supplier of GaAs epi wafer and other related products and services announced the new availability of size 2”&4” is on mass production in 2010. This new product represents a natural addition to PAM-XIAMEN’s product line.
Dr. Shaka, said, “We are pleased to offer GaAs LED epi wafer to our customers including many who are developing better and more reliable for Red Led. It includes AlGaInP led structure with multi quantum well, including DBR layer for LED chip industry, wavelength range from 620nm to 780nm by MOCVD. Therein, AlGaInP is used in manufacture of light-emitting diodes of high-brightness red, orange, green, and yellow color, to form the heterostructure emitting light. It is also used to make diode lasers.The availability improve boule growth and wafering processes.” and “Our customers can now benefit from the increased device yield expected when developing advanced transistors on a square substrate. Our led epitaxy on GaAs substrate are natural by products of our ongoing efforts, currently we are devoted to continuously develop more reliable products.”
PAM-XIAMEN’s improved AlGaInP led structure product line has benefited from strong tech support from Native University and Laboratory Center.
1. 610~630nm Red LED Reverse Polarity Structure
No.1 GaAs LED Wafer for Red Light
|Etch stop layer||InGaP: Si||–|
No.2 GaAs Red LED Epitaxy Wafer
Electro-optical Characteristics(Lf–=20 mA, 22℃）
|Model name||WD Code||WLD(λd, nm)||VF(Vf, V)||Reverse current(Ir, μA) Vr=-10V|
|Electro-optical Characteristics （@20deg. 20ma)|
Radiant Flux(Lf–=20 mA, 22℃）
|Radiant Flux(LOP, mcd)|
Above are reverse polarity structures, and we also can supply positive structure of GaAs LED wafer, detailed structure please consult us at [email protected].
The difference between the reverse polarity red light and the positive red light of LED is that the positive pole of the red chip is below and the negative electrode is on above. Therefore, the structure of positive LED wafer and reverse polarity LED wafer is different.
After the LED epitaxy wafer manufacturing process, the epitaxial wafer of GaAs-based LED is made in chip, the traditional red and yellow LED chips are soldered on the bracket with the positive electrode facing up and the negative electrode down. Later developed red and yellow LED chips have the negative electrode upward, and the positive electrode is installed in the reverse traditional direction on the bracket, which is called reverse polarity chip. The material and process of red and yellow reverse polarity LED chips are different from those of traditional red and yellow LED chips. The luminous efficiency of reverse polarity LED chips is higher than that of traditional polarity LED chips. Now the reverse polarity chip has become the mainstream of red and yellow LED chips.
In addition to the difference in luminous efficiency, the use method and specification of installed lamp beads are the same.
2. About GaAs Material
Gallium arsenide is used in the manufacture of devices such as microwave frequency integrated circuits, monolithic microwave integrated circuits, infrared light-emitting diodes, laser diodes, solar cells and optical windows.
GaAs is often used as a substrate material for the epitaxial growth of other III-V semiconductors including indium gallium arsenide, aluminum gallium arsenide and others.
Some electronic properties of gallium arsenide are superior to those of silicon. It has a higher saturated electron velocity and higher electron mobility, allowing gallium arsenide transistors to function at frequencies in excess of 250 GHz. GaAs devices are relatively insensitive to overheating, owing to their wider energy bandgap, and they also tend to create less noise (disturbance in an electrical signal) in electronic circuits than silicon devices, especially at high frequencies. This is a result of higher carrier mobilities and lower resistive device parasitics. These superior properties are compelling reasons to use GaAs circuitry in mobile phones, satellite communications, microwave point-to-point links and higher frequency radar systems. It is also used in the manufacture of Gunn diodes for the generation of microwaves.
Another advantage of GaAs is that it has a direct band gap, which means that it can be used to absorb and emit light efficiently. Silicon has an indirect bandgap and so is relatively poor at emitting light.
As a wide direct band gap material with resulting resistance to radiation damage, GaAs is an excellent material for outer space electronics and optical windows in high power applications.
Because of its wide bandgap, pure GaAs is highly resistive. Combined with a high dielectric constant, this property makes GaAs a very good substrate for Integrated circuits and unlike Si provides natural isolation between devices and circuits. This has made it an ideal material for monolithic microwave integrated circuits, MMICs, where active and essential passive components can readily be produced on a single slice of GaAs.
3. Standards for Gallium Arsenide LED Epi Wafer
The following standards apply to gallium arsenide phosphorous, gallium aluminum arsenide, aluminum gallium indium phosphorus and aluminum gallium indium nitrogen epitaxial wafers.
3.1 GaAs LED Epitaxial Wafer Surface Quality
The main influencing factor of the surface quality of AlGaInP / GaAs LED epitaxy is surface defects, and the maximum allowable value of the defects should meet the following requirements:
Maximum Allowable Value of Surface Defects
|Item||Maximum Allowable Value|
|Scratches||The length is less than the radius and 3 strips/cm2.|
|Point Defects With a Diameter ≤1mm||25/cm2|
|Point Defects With a Diameter ≥1mm||5/cm2|
|Note: The values in this table are applicable to non-surface roughened epitaxial wafers grown by metal organic chemical vapor deposition.|
3.2 Physical Structure Parameters of AlGaInP Epi Wafer on GaAs Substrate
The physical parameters of micro LED epitaxy wafer with AlGaInP / GaAs quantum well should be accord with the requirements in the table:
|Wavelength||Optical Fluorescence Peak Emission Wavelength||nm||x||x|
|The Wavelength When The Fluorescence Peak Is Emitted, The Standard Deviation On The Wafer||–||x||x|
|P-Type Electrode Contact Layer Doping Concentration||cm-3||x||x|
|N-Type Layer||N-Type Electrode Contact Layer Doping Concentration||cm-3||x||x|
|Note: “X” stands for specific value.|
3.3 Main Parameters of the LED Epitaxy Wafer with AlGaInP Epi Layer
The gallium arsenide LED epitaxy wafer main parameters should meet the parameters in the following table:
|Optical Parameters||Forward Voltage||V||x||x|
|Peak Emission Wavelength||nm||x||x|
|Spectral Distribution Bandwidth||nm||–||x|
|Radiant Power Retention Rate||%||x||x|
|Wafer Standard Deviation||Forward Voltage||–||–||x|
|Peak Emission Wavelength||–||–||x|
|Electrostatic Discharge Sensitivity||Electrostatic Discharge Sensitivity||–||x||–|
4. Q&A of Red LED Epi-wafer
Q1: I’m looking for red led epiwafer. Do you supply such products?
If yes, which wavelength, wafer size ?
A: You are welcome, your center ever ordered to us, and we also have received
hundreds of orders from universities in the world each year,
and now please see below: 4/ 2” Red LED epi-wafers 620+/-5nm
Q2: Concerning the wavelength what is the range available?
Finally, what is the susbtrate material ? Do you have any data sheet?
A: It is 2“size, wavelength: 620+/-5nm. The substrate material is GaAs.
Q3: I have a question, I understand that 620 nm is the only wavelength available?
A: 620nm is available, 445-475nm and 510-530nm is also avaible.
Q4: I request you to quote for one epitaxial wafer. We would like to have W/L:631nm – 636nm,λP is Typically 634nm-635nm. Would you advise me how you measure and guarantee λP W/L and no 2nd peak of IR W/L? Also how we make correlation between your side and our side ?
A: Please understand for red LED wafer, its stv itself is very small, normally it is within +/-2nm, even we can control it 633-635nm.
Q5: I have one question for you. What is the turn-on voltage of this device when it is contacted properly in GaInAlP LED wafer? Here we are contacting it using the GaAs substrate as Ground and the turn on voltage is about 9V.
A: Normally the turn-on voltage of the LED device based on InAlGaP LED epi wafer is 1.9-2.3v.
Q6: I am in the process of preparing a lab for the students. Our plan is etch a mesa down to the GaAs substrate and then place one contact on the top and ground contact on a chuck that is in intimate contact with the GaAs substrate. Do you think we can light emission with this configuration or do we have to contact the n layer directly?
A: Yes, GaAs LED epitaxy wafer can be lighting with your configurarion.
Q7: I was asking about the composition of the stack. In the diagram you sent me the top layer of the stack is GaP. My quiestion is: Is there a passivation oxide or nitride layer coated on top of the this top layer of GaP? Some times manufacturers put on this coating to protect the device wafer.
A: There is no any layer coated on the top the GaP layer of GaAs LED wafer.
Q8: Can I ask one last question about p type contact for the reverse polarity wafer? Can Mg-doped GaP (1570 nm thick region) be used as p-type contact region? I am not sure if it is possible to use 100 nm thick C-GaP region as contact region (it will be really hard to control the etch depth).
A: If you want ITO process for reverse polarity wafer, it is not workable, if it is gold process, it is ok.
Q9: Can I ask a question about the etching stop layer of the reverse polarity wafer? After wet etching of GaAs substrate, how should I remove the etching stop layer to expose the n GaAs contact layer?
A: 1/It is difficult to etch GaInP without damage to GaAs by wet etching.
2/ before usage, the red LED wafer with reverse polarity can be cleaned with acetone for xx minutes, or with a certain mixture (210120). Details please contact at [email protected].
Q10: I was trying to see if I can have a RED light out from the wafer using just putting a Indium chunk to the top of the wafer (GaP) and the side of the wafer, but I wasn’t able to see the red light coming out. Could you suggest a way to check Red light coming out?
A: It’s better to cut the red LED wafer into small pieces to measure, and the current can be increased a little bit. The whole piece is more difficult to measure
Q11: Yes, I cut the LED reverse polarity wafer into small piece and applied voltage range from 1 V to 10 V, I saw the current flowing but I could not see any light coming out. Is this normal?
A: It is suggested that at a current of 20 to 50 ma, the reverse polarity epitaxial wafer itself will light up and look a little weak, but it is impossible not to emit light
More about the LED epitaxy wafer on GaAs substrate please see:
AlGaInP LED Chip Sepcification
For more information, please contact us email at [email protected] and [email protected]