Xiamen Powerway Advanced Material Co.,Ltd., a leading supplier of GaN and other related products and services announced the new availability of size 2” is on mass production in 2017. This new product represents a natural addition to PAM-XIAMEN’s product line.
Dr. Shaka, said, “We are pleased to offer GaN substrate to our customers including many who are developing better and more reliable for GaN HEMTs, which have found immediate use in various wireless infrastructure applications due to their high efficiency and high voltage operation. Second generation technology with shorter gate lengths will be addressing higher frequency telecom and aerospace applications. Our GaN substrate has excellent properties, it’s a very hard, mechanically stable wide bandgap semiconductor material with high heat capacity and thermal conductivity. In its pure form it resists cracking and can be deposited in thin film on sapphire or silicon carbide, despite the mismatch in their lattice constants. GaN can be doped with silicon (Si) or with oxygen to n-type and with magnesium (Mg) to p-type; however, the Si and Mg atoms change the way the GaN crystals grow, introducing tensile stresses and making them brittle. Gallium nitride compounds also tend to have a high dislocation density, on the order of a hundred million to ten billion defects per square centimeter. 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 GaN substrate are natural by products of our ongoing efforts, currently we are devoted to continuously develop more reliable products.”
PAM-XIAMEN’s improved GaN product line has benefited from strong tech,support from Native University and Laboratory Center.
Now it shows an example as follows:
FS GaN substrate, n type, undoped: Resistivity<0.5 ohm.cm, carrier concentration: (1-5)E17
FS GaN substrate, n type, Si doped: Resistivity<0.5 ohm.cm, carrier concentration: (1-3)E18,
About Xiamen Powerway Advanced Material Co., Ltd
Found in 1990, Xiamen Powerway Advanced Material Co., Ltd (PAM-XIAMEN) is a leading manufacturer of compound semiconductor material in China. PAM-XIAMEN develops advanced crystal growth and epitaxy technologies, manufacturing processes, engineered substrates and semiconductor devices. PAM-XIAMEN’s technologies enable higher performance and lower cost manufacturing of semiconductor wafer.
Gallium nitride (GaN) is a binary III/V direct bandgap semiconductor commonly used in light-emitting diodes since the 1990s. The compound is a very hard material that has a Wurtzite crystal structure. Its wide band gap of 3.4 eV affords it special properties for applications in optoelectronic, high-power and high-frequency devices. For example, GaN is the substrate which makes violet (405 nm) laser diodes possible, without use of nonlinear optical frequency-doubling.
Its sensitivity to ionizing radiation is low (like other group III nitrides), making it a suitable material for solar cell arrays for satellites. Military and space applications could also benefit as devices have shown stability in radiation environments.Because GaN transistors can operate at much higher temperatures and work at much higher voltages than gallium arsenide (GaAs) transistors, they make ideal power amplifiers at microwave frequencies. In addition, GaN offers promising characteristics for THz devices
Q: Are your n-type FS GaN wafers natively n-type with that low resistivity below 0.5 Ohmcm? Or these wafers are already doped ones?. With that low resistivity one could realize a good ohmic contact on the back side of the wafer (please advice for the best metal combination if you know) which in this case should be fine grounded.
A: The situation would be below:
FS GaN substrate, n type, undoped: Resistivity<0.5 ohm.cm, carrier concentration: (1-5)E17, delivery time:20-30days
FS GaN substrate, n type, Si doped: Resistivity<0.5 ohm.cm, carrier concentration: (1-3)E18, delivery time: 50-70days.
Since few demand of Si doped one and large demand of undoped one, we use most of capacity to grow undoped one, which cause long delivery time of Si doped one.
Q: For double side polished wafer instead of a single side polished as we asked. We will definitely have several problems with this kind of wafer. First come with choosing the growth face (how to determine this?). The second comes with heating the substrate (this will reflect the radiation so a more temperature is needed)
A: Double side polished one has better flatness and much popular one, therefore we offer you double side polished, you can identify Growth face by flats easily, see below:
Q: Thank you for the information. The main problem with the double side polished wafers is the reflection of the heating radiation and hence the MBE manipulator should be warmed at a higher temperature to obtained the desired temperature on the opposite face of the substrate (that where the growth itself takes place). a grounded face absorbs more efficiently heat.
A: One solution is to coat molybdenum in the backside to deal with optical reflection absorbtion.
Q: Can I degas the wafer in the buffer chamber at 800 Celsius?
In MBE is a custom procedure to degas the wafers in the buffer chamber before introducing them in the growth chamber. The degassing can be done at different temperatures, the higher the better and the shorter. However, increasing temperature could deteriorate the surface (GaAs wafers are degassed at 400 Celsisus in the buffer but could be heat at 600 under As atmosphere in the growth chamber; Silicon could be degassed at 850 in the buffer etc.). The point is: which is the maximum temperature one can degas the GaN in the buffer chamber without affecting its surface (perhaps in the growth chamber the oxide removal temperature could be done at a higher temperature under nitrogen atmosphere)? Do you have such knowledge?
A: The best temperature for GaN degassed is between 750deg.-800deg. However, in 800 degree requires a very skilled operator to make sure the surface is not decomposition, therefore our propose temperature is 750 deg. Please see attached two pictures, which shows he surface RHEED pattern in different temperature( please review these two in order).
Q: To enhance heat transfer, we have been thinking to cover the backside of the wafer with 50 nm Ti deposited by e-beam. The Ti will be later use to build the backside ohmic contact of the future solar cells grown on top. What do you know about this procedure? Which is the best way to clean the wafer before this Ti deposition?
A: For the metal contact layer, an ICP etching process is suggested on the GaN surface before the deposition process.
Q: In the lack of an ICP process, how alse i could clean the FS GaN wafer before both the Ti deposition on the back side and for later growth by MBE? Do you you have any published paper explaining in detail the degassing/oxide surface removal (incorporating the nice RHEED pictures sent to us) and growth of GaN by MBE (you talk of growth temperatures above 750 but the literature is full of papers saying that the best growth temperatures for GaN is 700-740 by MBE? Now if I want to grow a GaN buffer on your FS GaN at which temperature should I grow this buffer?
A: IBE etching process is also suitable for the surface cleaning, however the etching thickness of GaN should be less than 100nm.
We didn’t publish these experimental results about the degassing process. As far as the growth temperature was concerned, it is strongly related to the atomic Nitrigon concentration of the different MBE growth system. The growth temperature could be higher with the higher N concentration, you can choose the suitable growth temperature according to the situation of your MBE system.
Key Words: GaN, GaN substrate, GaN layer, Gallium Nitride, GaN material