Semiconductor Optical Modulator With Type II Heterojunction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional semiconductor optical modulators with n-i-n structures face issues such as parasitic phototransistor effects due to hole accumulation in semi-insulating clad layers, leading to instability and modulation characteristic changes with light wavelength or intensity, and high driving voltages, which limit their operational range and stability.
Innovation Solution
A waveguide structure is designed with a first n-type semiconductor clad layer, a semiconductor core layer, and a second n-type semiconductor clad layer, where the electron affinity of the clad layer is smaller than that of the second n-type clad layer, forming a type II heterojunction to create a potential barrier for electrons, and p-type semiconductor regions are introduced to draw holes away from the clad layer, reducing leak current and voltage loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional n-i-n structure optical modulator is used, then the device can operate as an optical modulator, but hole accumulation in the semi-insulating clad layer causes parasitic phototransistor effects leading to instability and modulation characteristic changes
Solution Approach 1:
The patent extracts and removes the harmful semi-insulating clad layer that causes hole accumulation and parasitic phototransistor effects. By replacing it with a fully n-type clad layer structure, the harmful element is eliminated while maintaining the essential optical modulator functionality.
Solution Approach 2:
The patent changes the doping parameter of the clad layer from semi-insulating to fully n-type. This parameter change prevents hole accumulation by ensuring both electrons and holes are efficiently collected by the electrodes, thereby eliminating the parasitic phototransistor effect and improving operational stability.
2Device complexity
If a conventional n-i-n structure optical modulator is used, then the device structure is simple, but high driving voltage is required leading to increased power consumption
Solution Approach 1:
The patent changes the doping configuration parameter from n-i-n to fully n-type structure. This parameter change improves the electrical field distribution and reduces the driving voltage requirement, thereby lowering power consumption while maintaining structural simplicity.
3Loss of energy
If the clad layer electron affinity is increased, then the potential barrier for electrons is reduced, but hole accumulation in the clad layer increases causing instability
Solution Approach 1:
The patent changes the doping type parameter of the clad layer from semi-insulating to fully n-type. This parameter change simultaneously addresses both electron loss and hole accumulation issues by ensuring efficient collection of both charge carriers by the electrodes, thereby reducing energy loss while maintaining modulation stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration achieves stable operation with low-loss and excellent voltage-current characteristics, reducing frequency dispersion and maintaining modulation stability across varying light conditions, enabling high-speed and low-voltage operation.
Implementation Method 1
the electron affinity of the semiconductor clad layer is smaller than that of the second n-type semiconductor clad layer... forming a type II heterojunction to create a potential barrier for electrons
Implementation Method 2
p-type semiconductor regions are introduced to draw holes away from the clad layer, reducing leak current and voltage loss
Implementation Method 3
a semiconductor optical modulator including a waveguide structure... and a semiconductor core layer having an electro-optic effect... A phase modulator which modulates a phase of light by changing a refractive index
Data Source
AI summary
There is provided a semiconductor optical modulator capable of performing a stable operation and having an excellent voltage-current characteristic to an electric field while exhibiting the characteristic of a semiconductor optical modulator with an n-i-n structure. The semiconductor optical modulator includes a waveguide structure that is formed by sequentially growing an n-type InP clad layer (11), a semiconductor core layer (13) having an electro-optic effect, a p-InAlAs layer (15), and an n-type InP clad layer (16). An electron affinity of the p-InAlAs layer (15) is smaller than an electron affinity of the n-type InP clad layer (16). In the waveguide structure having such a configuration, a non-dope InP clad layer (12) and a non-dope InP clad layer (14) may be respectively provided between the n-type InP clad layer (11) and the semiconductor core layer (13), and between the semiconductor core layer (13) and the p-InAlAs layer (15).