NEWS ANALYSIS Kyma reveals ammonothermal-HVPE
GaN growth plans Kyma teams up with Ammono and Avogy to advance novel bulk GaN growth.
LATE LAST YEAR, US-based wide bandgap materials supplier, Kyma Technologies, won $3.2 million from DoE agency, Advanced Research Projects Agency-Energy (ARPA-E), to develop high quality GaN substrates. Joining forces with Poland-based bulk GaN pioneer, Ammono, as well as US power electronics developer, Avogy, Kyma intends to pioneer a novel growth process to deliver the low cost, high performing GaN boules that power electronics manufacturers crave.
The project is ambitious but with Kyma chief executive, Keith Evans, describing the industry line-up as “the dream team”, those involved expect success. So what lies in store?
The Kyma team will first combine Ammono’s ammonothermal growth process with its HVPE-growth process to grow high quality boules quickly. Without a doubt, ammonothermal growth creates higher structural quality wafers than HVPE growth alone, but takes time. And as Kyma’s chief science officer, Jacob Leach, puts it: “We want to get the structural quality of the ammonothermal process with the high growth rate of HVPE.”
To date, most manufacturers of GaN substrates, including Kyma, grow GaN wafers by HVPE on a non-native seed such as sapphire. But while the process is quick, it is not simply extendable to boule growth due to lattice and thermal expansion mismatch between the GaN and the non-native seed.
So with this in mind, Leach and colleagues will take a high structural quality seed GaN wafer, grown by Ammono, and rapidly grow GaN layers on it by HVPE. Their initial aim is to replicate the structural quality of the
seeds it’s of the order of around a kilometre, while the radius of curvature in our HVPE seeds is about 2 m to 10 m,” he says. “It would be tough to take an HVPE seed and grow very thick boules by HVPE, so we want to marry these two processes.”
Kyma’s chief science officer, Jacob Leach, beside a Veeco Wyko optical surface profilometer that is used for investigating surface morphology and defects in as-grown plus post polished materials.
ammonothermal seed using HVPE, and then create GaN overlayers with lower impurity concentrations and point defect densities than in the original seed.
“We aim to have two inch thick boules that we’ve not only grown, but also demonstrated the ability to slice and polish; we want to make real substrates,” says Leach. “We will deliver these to our device partner, Avogy, who will make vertical diodes using their processes, to demonstrate the utility of these substrates.”
Close collaboration between the key GaN industry players offers clear appeal, but why is Kyma growing its GaN layers on an Ammono-grown wafer; why not use an HVPE-grown free-standing GaN wafer as the seed? As Leach explains, GaN seed wafers produced by HVPE on sapphire suffer from lattice lensing. Here, the crystalline lattice is curved across the wafer, which changes the local mis-cut across the wafer.
“If you measure the radius of curvature in the lattice of Ammono’s ammonothermal
18
www.compoundsemiconductor.net March 2014
If successful, the team intends to launch a two-inch commercially viable product by the end of the project, some four years away. Not a modest task, but Kyma chief executive, Evans, believes this is achievable. As he highlights, Kyma is not starting from scratch, but has carried out GaN-on-GaN growth in the past. And, what’s more, he is very excited about combining the ammonothermal and HVPE growth processes.
“There have been academic studies about this and Kyma has been talking about it for years,” he says. “But to the best of my knowledge, this is the first time that two commercial entities have done this.”
Evans firmly believes that high structural quality boules are crucial to driving down GaN wafer costs and provide the only route to manufacturing economies of scale. Indeed, silicon, GaAs, InP, germanium and most sapphire substrates are made by slicing from a boule.
And now he hopes the Ammono- Kyma-Avogy combo will provide the winning formula.“We’ve picked the best structural quality GaN maker, plus our HVPE process and the best vertical GaN power electronics developer to make a great team,” he says “You know Robert Dwilinski [Ammono] and I have been thinking about this for half a decade, and as I have said; ‘they have the seed and we have the speed’.”
`
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132 |
Page 133 |
Page 134 |
Page 135 |
Page 136 |
Page 137 |
Page 138 |
Page 139 |
Page 140 |
Page 141 |
Page 142 |
Page 143 |
Page 144 |
Page 145 |
Page 146 |
Page 147 |
Page 148 |
Page 149 |
Page 150 |
Page 151 |
Page 152 |
Page 153 |
Page 154 |
Page 155 |
Page 156 |
Page 157 |
Page 158 |
Page 159 |
Page 160 |
Page 161 |
Page 162 |
Page 163 |
Page 164