You can sometimes clear the gap zone from defect states known as dangling bonds in amorphous semiconductor materials by adding hydrogen., to satúrate such bonds.

A dangling bond is like a chemical bond attached to nothing.

This may change the band gap a bit.

Mr. Guillemoles, 

             Thanks for your reply. I appreciate your valuable inputs here. 

 Regards. 

Mr. Weisz,

          Thanks for your reply. Yes indeed hydrogenation is an well known method to passivate the dangling bond in amorphous Si material, though it cannot completely eliminate it.  But my inquiry is does shrinking or enlargement of band gap have any direct or indirect influence on the defect states reside within the band gap (like their position or energy distribution or capture cross section etc.), which are responsible for  sub band gap optical absorption.   

Hi,

you should read about "thermoluminescence materials and method", which give more information of band gap and local energy levels of host and guest (or defects) in semi-conductor and dielectric.

Hi Bazlul,

Since the defect level usually does not follow the shift of the band edge, either conduction band or valence band, when the bandgap is changed, the relative position of the defect level to the band edge is also changed, but to different extent, depending on the specific defect type.

You can find one example for a close tracking of the shifts of the band edge and the impurity level with varying bandgap (see the attached paper).

To

Yong Zhang

      Thank you very much for your response and the attachment. It's really valuable. I appreciate it. 

 Regards. 

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 To

 N.T.Tanah

     Thanks a lot  for your valuable suggestion. 

Regards.

The correlation between defect states and band gap scales with defect (or surface states[1] or/and doping[2-3]) density. Upon intercalation like processes this correlation becomes stronger, since the intercalants' density might extent in a wider (towards a bulk) scope. So, the initial (low concentration) states might convert to a collective (bulk) property[3,4], e.g. the correlation increases with the (high, and variable) intercalants' density.

1.  Fermi Level of Surface States in TiO2 Nanoparticles    http://www.elp.uji.es/paperspdf/2003%20NL%20Fermi.pdf  ;    

2.  http://www.uwyo.edu/cpac/_files/docs/kasia_lectures/2-intrinsicanddopedsemiconductors.pdf

3.  First-principles investigation of dual substitutional impurity-induced electronic structural modulation of PbTe on cationic and anionic sites     http://www.sciencedirect.com/science/article/pii/S1359645413005235#

4.  Shift of the Fermi Level during co-intercalation of Copper and Iron into TiSe2    https://link.springer.com/article/10.1134/S1063783410080032

Ioannis Samaras, 

          Thank you very much for your answer and the materials you have attached. Sir, do you think this correlation you have mentioned above  in the context of external doping (mentioned in your attached papers) is equally applicable for undoped or unintensionally doped semiconductors when they are subjected to processing methods like thermal annealing ?  

Regards. 

In common thermal annealing of doped semiconductors, atoms migrate in the crystal lattice and the number of dislocations decreases, etc., often, leading to weak changes in some surface[1] and electronic[2] properties of semiconductors and their interfaces[3]. Also, peculiar thermal annealing might offer in several, more drastic (morphological and electronic) modifications[4-7]. However, the un-intentionally doped semiconductors is another huge topic, mainly, in the class of the intercalation compounds[8,9].

1.  Impact of Thermal Processing on Silicon Wafer Surface Roughness    http://www.sunedisonsemi.com/assets/file/technology/papers/2008-E11-0516O-v071708.pdf

2.  Influence of rapid thermal processing on carrier concentration in high resistivity silicon    http://onlinelibrary.wiley.com/doi/10.1002/pssa.201700275/epdf

3.  Effects of oxygen thermal annealing treatment on formation of ohmic

contacts to n-GaN   http://aip.scitation.org/doi/full/10.1063/1.4769965

4.  Influence of the Position of the Fermi Level on an Infrared Active Defect in Irradiated Silicon    http://iopscience.iop.org/article/10.1088/0256-307X/12/5/009/pdf

5.  Optical properties of uniformly sized silicon nanocrystals within a single silicon oxide layer   https://link.springer.com/content/pdf/10.1007%2Fs11051-013-1538-0.pdf

6.  Effect of thermal annealing on properties of polycrystalline ZnO thin films   http://www.sciencedirect.com/science/article/pii/S0022024816303815

7.  Effect of Thermal Annealing on Band Edge Absorption Spectrum of Arsenic-Ion-Implanted GaAs  http://iopscience.iop.org/article/10.1143/JJAP.40.6226/pdf

8.  Tunable Se vacancy defects and the unconventional charge density wave in 1T−TiSe2−d    https://journals.aps.org/prb/abstract/10.1103/PhysRevB.95.045310

9.  Science and technology roadmap for graphene, related 2-dim crystals, and hybrid systems    http://pubs.rsc.org/en/Content/ArticleLanding/2015/NR/C4NR01600A#!divAbstract