Semiconductor Optical Device Zn Diffusion Barrier
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Solution Overview
Problem
The crystallinity of semiconductor laser devices is deteriorated due to the diffusion of Zn p-type dopant into undoped active layers and the low-temperature growth requirements for C p-type doping, which increases threshold current values and reduces optical output.
Innovation Solution
Forming a Zn-doped InGaAlAs layer with favorable crystallinity between the C-doped InGaAlAs upper-side guiding layer and the undoped active layer, and using a C-doped InAlAs layer to suppress Zn diffusion, while optimizing growth conditions to minimize crystallinity deterioration and growth interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If Zn concentration in p-type cladding layer is increased to enhance laser characteristic, then laser threshold is reduced, but Zn diffuses into undoped active layer and laser characteristic is sharply deteriorated
Solution Approach 1:
A C-doped InGaAlAs layer is introduced as an intermediary barrier between the Zn-doped InP cladding layer and the undoped active layer. This intermediate layer effectively blocks Zn diffusion into the active layer while maintaining laser performance, resolving the contradiction between enhancing laser characteristic and preventing harmful Zn diffusion.
2Object-generated harmful factors
If C is used as p-type dopant with high doping concentration to suppress Zn diffusion, then Zn diffusion is blocked, but growth temperature must be set to 600°C or less and crystallinity is deteriorated
Solution Approach 1:
The patent uses a composite structure of C-doped InGaAlAs layer combined with Zn-doped InP cladding layer. The InGaAlAs matrix provides a more stable crystalline structure that can accommodate C doping at higher temperatures (up to 700°C) compared to pure InP or InGaAs, thus suppressing Zn diffusion while maintaining good crystallinity through material composition optimization.
3Object-generated harmful factors
If C-doped layer is grown at low temperature of 600°C or less to achieve high C doping concentration, then Zn diffusion is suppressed, but growth interruption is necessary and crystallinity at interface is deteriorated
Solution Approach 1:
The patent optimizes the composition parameters of the InGaAlAs layer (specifically the Al content and InGaAlAs ratio) to enable C doping at higher growth temperatures up to 700°C. By changing the material composition parameters, the patent avoids the need for growth interruption and maintains good interface crystallinity while still achieving effective Zn diffusion suppression.
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 approach reduces the deterioration of crystallinity near the active layer, suppresses Zn diffusion, improves manufacturing yield, reduces threshold current values, and increases optical output.
Implementation Method 1
Zn used as the p-type dopant easily diffuses. Accordingly, for example, when the concentration of Zn of a p-type guiding layer or a p-type buried layer is increased, the laser characteristic is enhanced up to a certain concentration of Zn along with the increase of the concentration of Zn. However, when the concentration of Zn becomes excessively high, Zn diffuses into an undoped active layer and hence, the laser characteristic is sharply deteriorated.
Implementation Method 2
As a method of crystal growth on an InP substrate for a semiconductor laser, a metalorganic vapor phase epitaxy has been mainly used.
Implementation Method 3
When C is doped with a high doping concentration, it is necessary to allow C to grow at a low temperature of 600° C. or less and at a low V/III ratio. Thus, the crystallinity of the InGaAlAs upper-side guiding layer 5 is deteriorated.
Data Source
AI summary
The object of the invention is to reduce the deterioration of crystallinity in the vicinity of an active layer when C, which is a p-type dopant, is doped and to suppress the diffusion of Zn, which is a p-type dopant, into an undoped active layer, thus to realize a sharp doping profile. When a Zn-doped InGaAlAs layer having favorable crystallinity is provided between a C-doped InGaAlAs upper-side guiding layer and an undoped active layer, the influence of the C-doped InGaAlAs layer whose crystallinity is lowered can be reduced in the vicinity of the active layer. Further, the Zn diffusion from a Zn-doped InP cladding layer can be suppressed by the C-doped InGaAlAs layer.