InGaN (Indium Gallium Nitride) epi-wafer with MQWs is provided, which is a light-emitting layer for fabricating blue or green LED. Indium gallium nitride is a mix material of gallium nitride and indium nitride and often grown on GaN buffer on sapphire, silicon or SiC substrate. Researches carried out by PAM-XIAMEN, a GaN epi wafer manufacturer, are found that by changing the indium concentration in the InGaN compound, the color of the light emitted by the LED can be changed, possibly covering the entire visible light spectrum.
InGaN epi-wafer
1. GaN Epi-wafer 2 Inch
PAM190611-LED
| Orientation | C(0001) 0.2±0.1 grad. to m-axis (right relative to the OF); |
| 0±0.25 grad. to a-axis (drawing) | |
| Diameter | 50.8±0.15 mm |
| Thickness | 430±10 um |
| Substrate profile: | — |
| Shape | Cone |
| Width | 2.7 um |
| Height | 1.7 um |
| Step | 0.3 um |
| Front side | Polished, epi-ready (Ra<0.3 nm) |
| Back side | polished 1.0um |
| Grade | optical |
| OF length | 16±1 mm |
| OF orientation | a-axis ±0,25 grad |
| Bow | < 10 um |
| TTV | < 5 um |
| Warp | < 10 um |
| Chamfer | sharp edges are blunted |
| Laser marking | On back side |
2. Main Parameters of InGaN Epitaxial Wafer
| Parameter | Characteristics | ||
| Min. | Typ. | Max. | |
| Thickness р-GaN, um | — | — | — |
| CC р-GaN, cm-3 | — | — | — |
| Mobility p-GaN, cm2/ V·s | 30 | — | — |
| Thickness n-GaN layer, um | — | — | — |
| CC n-GaN, cm-3 | — | — | — |
| Mobility n-GaN, cm2/ V*s | 300 | — | — |
| Total thickness GaN, um | 5 | — | 7 |
| PLFWHM, nm | — | — | 22 |
| WLD, nm | 455 | — | 460 |
| Dispersion of WLD, nm | — | — | 5 |
| Forward voltage (@ 350 mA), V | 2.8 | — | 3.4 |
| Reverse voltage (@ 10 uA), V | 13 | — | 17 |
| Total emitting power (@ 350 mA), mW | 400 | — | 600 |
3. GaN Epi Standards for LED
The surface defects of the indium gallium nitride LED epitaxial wafer should meet the requirement in the table:
| Item | Maximum Allowable Value for 2 Inch | Maximum Allowable Value for 4 Inch |
| Scratches | Length ≤10mm and quantity ≤10
Length ≤10mm and quantity ≤2 |
Length ≤10mm and quantity ≤15
Length ≤10mm and quantity ≤4 |
| Tiny Pits or Particles (Dia <1mm) | 200 pcs | 400 pcs |
| Large Uneven Surface (Dia > 1mm) | 50 pcs | 200 pcs |
| Stains, Fingerprints | Occupied area ≤5% | Occupied area ≤5% |
The requirements for the performance of InGaN epi wafer are listed in the table:
| Parameters | Requirements | ||
| Diameter (mm) | 50.8 ± 0.1 | ||
| Performance parameters | Dominant wavelength range λ n (nm) | Blue Light: 440-480 | Green Light: 500-540 |
| Luminous Intensity (mcd) | ≥25 | ≥250 | |
| Forward Voltage | Under 20mA forward current, not higher than 3.5 V | ||
| Reverse Current | Under reverse voltage -8V, not higher than 2.0 uA | ||
| Electrostatic Discharge Susceptibility Test | Not lower than human body model 1000V | ||
| On-chip Standard Deviation | Dominant Wavelength | ≤5 % | |
| Light Intensity | ≤10 % | ||
4. Main Difficulties for GaN Wafer Technology with Multiple Quantum Well
The band gap of nitride semiconductor is larger than that of phosphide, which will greatly improve the thermal stability of optical properties in the device. Therefore, InGaN is the most important and indispensable material for the preparation of light-emitting devices. And the GaN epi wafer market is growing with the development of GaN epitaxy technology. However, the preparation of InGaN / GaN multiple-quantum well light emitting diode wafer still has the following problems:
4.1 Phase Separation of InGaN Epitaxial Layer on GaN Wafer Substrate
Unstrained InGaN layer have great InN incompatibility in GaN, and high-quality, high-In content (>25%) InGaN is difficult to grow, hindering the preparation of high-efficiency InGaN LED with long-wavelength. At the standard growth temperature of InGaN (700°C-900°C), gallium nitride can only absorb a few percent of In. In-rich wafers are unstable when thermally annealed at higher temperatures, and the InGaN layer is easily decomposed. Both experimental and theoretical studies have shown that the higher the In composition, the easier the phase separation of the InGaN epi-layer on GaN is. Therefore, avoiding phase separation is a problem that needs to be considered for the growth of InGaN on GaN epi wafer with high In content.
4.2 Lattice Mismatch between InGaN and GaN Epi Wafer
There is a large lattice mismatch between InGaN and GaN. The lattice mismatch becomes more significant with the increase of In composition. In blue lasers, the lattice mismatch between InGaN quantum wells and GaN reaches 1.6%. In the green laser, it reaches 3.3%. Severe lattice mismatch can cause crystal defects, decrease of radiation efficiency, and shorten the life of the laser in the InGaN / GaN quantum well.
4.3 Polarity Selection for InGaN / GaN Epi-wafer Growth
Most of GaN epiwafer supplier grows InGaN/GaN heterostructures along the (0001) plane. Due to the changes in surface chemical bonds, the In-doping efficiency in InGaN quantum well may vary significantly depending on the wafer crystal orientation. The incorporation of H and O impurities in semi-polar and non-polar InGaN will be higher, while the polarity of the InGaN film is usually rough. At the same time, in terms of controllability of material growth and crystal quality, InGaN film on gallium nitride wafer with metal polarity generally have greater advantages. In order to obtain a high-quality, high-In composition InGaN epitaxial layer, people have to make a trade-off between polarity and crystal quality. Therefore, the choice of polarity is one of the important problems faced by InGaN epi wafer growth with high quality and high In content.
For more information, please contact us email at victorchan@powerwaywafer.com and powerwaymaterial@gmail.com