You can calculate the density of dislocations by X-ray diffraction w-scan rocking curve of the (002) plains for screw dislocations and the w-scan of asymetric plains such as (101) plains. Check the next reference:

Comparative study of threading dislocations in GaN epitaxial layers by nondestructive methods , Volume 57, January 2017, Pages 32-38

The pits can be estimated by counting its density by AFM.

The tramps can be studied by Deep-level transient spectroscopy.

Also luminescence can give you an idea of the crystal quality and deep defects.

Moreover you can measure the concentration of impurities such as Oxigen and Carbon by SIMS.

Finally Hall effect mobility can tell you the scattering mechanisms such as dislocations related to the defects in your film.

I hope this will be useful for you.

regards

Dear K. Dasari,

The defect density can be directly calculated using cross sectional TEM (or STEM) imaging. But in this method, during imaging only small area of the specimen is considered and determination of true value of dislocation density is difficult. In this situation, you should perform XRD (rocking curve) measurements and determine the FWHM of the characteristic peaks in XRD profiles (caused by the reflection of different planes). It indicates larger broadening of FWHM is associated with larger defect density. But, you should also carefully consider the other probable reasons of increase of the magnitude of FWHM.

With best regards,

Anjan

What kind of defects do you want to calculate?

Density of Dislocations?

Stacking faults?

Pits?

Point defects?

Tell us in order to help you.

Regards

Helo @carlos Hernandez,

Thanks for the response.

I am trying to measure all kinds defects.

You can calculate the density of dislocations by X-ray diffraction w-scan rocking curve of the (002) plains for screw dislocations and the w-scan of asymetric plains such as (101) plains. Check the next reference:

Comparative study of threading dislocations in GaN epitaxial layers by nondestructive methods , Volume 57, January 2017, Pages 32-38

The pits can be estimated by counting its density by AFM.

The tramps can be studied by Deep-level transient spectroscopy.

Also luminescence can give you an idea of the crystal quality and deep defects.

Moreover you can measure the concentration of impurities such as Oxigen and Carbon by SIMS.

Finally Hall effect mobility can tell you the scattering mechanisms such as dislocations related to the defects in your film.

I hope this will be useful for you.

regards

Dear Kiran,

If you are using TEM for defect characterisation then the best technique is Diffraction contrast experiments (2-beam conditions). Depending on the growth orientation of your film (polar, semipolar, nonpolar) you may need samples along both in plane directions as well as a plan view sample for a complete characterisation.

From each direction's zone axis, you can choose to image with reflections that correspond to defects with different Burger's vectors and by using the g.b invisibility criterion you can attribute the density you measure to a specific type of defect (e.g. using g 0002, perfect dislocations with c or a+c mixed Burgers vector as well as some partials are visible). If you use two non equivalent reflections from each direction, you can have a pretty accurate measurements for different types of dislocations and stacking faults.

There's a plenty of literature on the subject.

Hope this was useful.

In addition to: The pits can be estimated by counting its density by AFM.

I would make a selective etching of GaN before counting the pits by AFM or SEM.

Wet etching of GaN, AlN, and SiC: a review

or the papers of Jan Wayer.

Sorry J.L.Weyher

Article Characterization of wide-band-gap semiconductors (GaN, SiC) ...