GB/T 36705-2018Test method for carrier concentration of gallium nitride substrates—Raman spectrum method (English PDF)

Foreword

This standard was drafted in accordance with the rules given in GB/T 1.1-2009.

This standard was jointly proposed and is managed by the National Semiconductor Equipment and Materials Standardization Technical Committee (SAC/TC203) and its Technical Subcommittee on Materials (SAC/TC203/SC2).

1 Scope

This standard specifies a method for testing the carrier concentration of an N-type gallium nitride substrate by Raman spectroscopy.

This standard applies to the test of the carrier concentration of N-type gallium nitride substrate grown on sapphire, silicon carbide, silicon, gallium nitride materials.

Test range: 1 x 10^17 cm^-3 to 1 x 10^20 cm^-3.

2 Normative references

The following documents are indispensable for the application of this document. For dated references, only dated versions apply to this document. For undated references, the latest edition (including all amendments) applies to this document.

GB/T 4326 extrinsic semiconductor single crystal Hall mobility and Hall coefficient measurement method

GB/T 8170 Numerical Rounding Rules and Representation and Determination of Limit Values

GB/T 14264 semiconductor material terminology

3 Terms and definitions

The terms and definitions defined in GB/T 14264 apply to this document.

4 Method summary

At a certain temperature, the atoms in the material lattice vibrate slightly near their equilibrium positions (lattice vibration), and the energy of the lattice vibration is represented by phonons. A certain concentration of carriers in the gallium nitride material interacts with the lattice vibration to form a coupling of longitudinal optical phonons and carriers, the LO phonon-plasmon coupled mode (LOPC), which exhibits low-frequency and high-frequency characteristic peaks in the Raman spectrum (lower and upper frequency branches, often labelled LPP- and LPP+).

The peak position of the characteristic peaks changes with the carrier concentration, and the carrier concentration can be calculated from the change of the peak position. The method allows a micro-area test of the carrier concentration of N-type gallium nitride substrates by Raman spectroscopy, with a measured spot diameter of 0.7 µm to 2 µm.

5 Interference factors

5.1 Raman spectroscopy is commonly used to detect stress in thin film materials, so it is necessary to consider the effects of stress introduced during testing. When the carrier concentration is low (about < 3 x 10^17 cm^-3), the carrier concentration is calculated from the peak position of the polar phonon mode A1 (LO); in order to eliminate the effect of stress on the A1 (LO) peak position, the stress state of the sample can be calibrated using the E2H peak position in the Raman spectrum of the gallium nitride material.

The shift of the polar phonon mode A1 (LO) peak position due to stress is derived according to formula (1).