Semiconductor device manufacturing: process – Introduction of conductivity modifying dopant into... – Ion implantation of dopant into semiconductor region
Patent
1997-10-28
2000-02-22
Chaudhari, Chandra
Semiconductor device manufacturing: process
Introduction of conductivity modifying dopant into...
Ion implantation of dopant into semiconductor region
438 22, 438 45, 438 46, H01L 2122
Patent
active
060279893
DESCRIPTION:
BRIEF SUMMARY
This invention relates to semiconductor heterostructures and, more specifically, to a method of bandgap tuning a quantum well structure in a spatially selective manner.
The invention can also be applied to post processing to modify device properties. The invention provides a useful and new method for the monolithic integration of multi-use devices on a single substrate with simplified growth topology.
Optical and electrical properties of quantum well structures are of great importance for novel semiconductor device applications. The ultimate goal of monolithic integration of optical, optoelectronic and electronic components requires the capability for controllable lateral and vertical modifications of optical constants and electrical characteristics in such components.
Present techniques include etching and regrowth. Regrowth involves growing a device structure such as a laser, and then etching away the regions where other components, such as modulators etc., are desired and regrowing these components. This involves a large number of processing steps, with problems associated with growing good quality material after etching, leading to poor device yields.
U.S. Pat. No. 5,238,868 describes in detail. a technique for shifting the bandgap using quantum well intermixing. This technique involves mixing quantum well material with surrounding barrier material to change the bandgap of the quantum well. This is performed by introducing impurities or defects into the quantum well in the region of the wafer that requires a modification of the bandgap. The implanted wafer is then annealed to intermix the defects and shift the bandgap. This technique does not, however, permit different regions of the wafer to be selectively tuned.
An object of the invention is to alleviate these problems.
According to the present invention there is provided a method of bandgap tuning a quantum well heterostructure wherein ions are implanted into the heterostructure to create defects therein, and the heterostructure is then thermally treated, e.g. annealed, to initiate intermixing in the quantum well region, characterized in that different regions are implanted with ions in a spatially selective manner to create different concentrations of defects and thereby result in different bandgap shifts during subsequent treatment.
Tuning the bandgap of a quantum well structure during subsequent thermal treatment in a spatially selective manner in this way is a powerful technique for performing monolithic integration. This allows the fabrication of lasers (of many wavelengths), detectors, waveguides, modulators, etc. on a single wafer.
In one embodiment, the ions are implanted through a mask, for example of SiO.sub.2, of varying thickness at a single energy, for example, of about 1 MeV. This varies the energy of ions reaching different regions, resulting in different concentrations of defects in the semiconductor. A thin SiO.sub.2 layer will slow down the ions so that they will reach the surface of the semiconductor slower than they would in the absence of the mask, and hence will result in a smaller bandgap shift. A very thick mask will stop the ions completely and will result in no shift. Therefore, by varying the thickness of the mask, the degree of damage can be controlled. The mask may be removed prior to thermal treatment, although this is not necessary.
In another embodiment, the ions are implanted through a mask of varying density to achieve a similar result. In other embodiments, alternative techniques are employed to vary the dosage in a spatially selective manner.
The inventive technique works because of dependence of the shift in quantum well bandgap on defect concentration, which in turn is dependent on ion energy and/or dosage. The greater the dose, or the higher the energy of the implanted ions, the more damage that will be done. This invention provides the enabling technology for the integration and modification of optoelectronic components on a monolithic structure.
The invention also provides an apparatus for bandgap tuning a qu
REFERENCES:
P.G. Piva et al., "Bandgap tuning of semiconductor quantum well structures using ion implantation," Superlattices and Microstructures, 15 (4), pp. 385-390 (no month given), 1994.
L.A. Coldren et al., Diode lasers and photonic integrated circuits, John Wiley and Sons, pp. vii-xv (no month given), 1995.
Aers Geofrey C.
Charbonneau Sylvain
Davies Michael
Koteles Emil S.
Poole Philip J.
Chaudhari Chandra
Christianson Keith
National Research Council of Canada
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