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5 InGaN/GaN Multiple Quantum Wells Materials …
Polarization effect and quantum confined Stark effect in InGaN/GaN multiple
quantum wells materials become even more obvious with the increase of In incorporation. The development of semi-polar and non-polar LEDs can effectively alleviate
these effects on nitride LEDs performance.
This chapter mainly introduces the polarization effects, quantum confined Stark
effect, and carrier localization effect closely related to the InGaN/GaN multiple
quantum wells materials. The effects of these properties on blue and green LEDs
will be also discussed. Finally, a brief overview of the research on semi-polar and
non-polar LEDs is provided.
5.1 Introduction to InGaN Material System
The InGaN material is a ternary alloy composed of GaN and InN. The energy gap
of this material is tunable from 0.7 to 3.4 eV with a very wide spectral range as
shown in Fig. 5.1. As can be seen from the figure, the spectra cover the green, blue
and ultraviolet. InGaN material has high breakdown voltage and stable chemical
properties. These properties make it possible to achieve high efficiency blue and
green LEDs.
The emission wavelength of InGaN/GaN multi-quantum wells LEDs can adjusted
in two ways: one is to change the well width and the number of wells in the quantum
well or the thickness of the barrier layer, and the other is to adjust the composition
of In in the active layer of InGaN alloy. It is easier to achieve and control different
luminescence wavelengths by adjusting the composition of In in the InGaN alloy.
The In composition can be adjusted by controlling the flow rate of the carrier gas
ratio of TMIn and TMGa during the MOCVD growth process. Theoretical analysis
shows that the emission wavelength of InGaN LED belongs to the blue light category
when the composition of In is 15–20%. When the composition of In is 25–30%, the
emission wavelength of InGaN LED belongs to the green light category. Generally,
in order to extend the emission wavelength to the rest of the visible light wavelength,
it is necessary to configure the In composition to a large extent to change the bandgap.
However, it causes an excessive lattice mismatch, accompanied by a higher order
Fig. 5.1 Wavelength range corresponding to LEDs of different materials [3]
5 InGaN/GaN Multiple Quantum Wells Materials …
Polarization effect and quantum confined Stark effect in InGaN/GaN multiple
quantum wells materials become even more obvious with the increase of In incorporation. The development of semi-polar and non-polar LEDs can effectively alleviate
these effects on nitride LEDs performance.
This chapter mainly introduces the polarization effects, quantum confined Stark
effect, and carrier localization effect closely related to the InGaN/GaN multiple
quantum wells materials. The effects of these properties on blue and green LEDs
will be also discussed. Finally, a brief overview of the research on semi-polar and
non-polar LEDs is provided.
5.1 Introduction to InGaN Material System
The InGaN material is a ternary alloy composed of GaN and InN. The energy gap
of this material is tunable from 0.7 to 3.4 eV with a very wide spectral range as
shown in Fig. 5.1. As can be seen from the figure, the spectra cover the green, blue
and ultraviolet. InGaN material has high breakdown voltage and stable chemical
properties. These properties make it possible to achieve high efficiency blue and
green LEDs.
The emission wavelength of InGaN/GaN multi-quantum wells LEDs can adjusted
in two ways: one is to change the well width and the number of wells in the quantum
well or the thickness of the barrier layer, and the other is to adjust the composition
of In in the active layer of InGaN alloy. It is easier to achieve and control different
luminescence wavelengths by adjusting the composition of In in the InGaN alloy.
The In composition can be adjusted by controlling the flow rate of the carrier gas
ratio of TMIn and TMGa during the MOCVD growth process. Theoretical analysis
shows that the emission wavelength of InGaN LED belongs to the blue light category
when the composition of In is 15–20%. When the composition of In is 25–30%, the
emission wavelength of InGaN LED belongs to the green light category. Generally,
in order to extend the emission wavelength to the rest of the visible light wavelength,
it is necessary to configure the In composition to a large extent to change the bandgap.
However, it causes an excessive lattice mismatch, accompanied by a higher order
Fig. 5.1 Wavelength range corresponding to LEDs of different materials [3]