InGaN epi-wafers

InGaN epi-wafers

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 / GaN epi wafer

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.

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