Optical Spectroscopy of Hydrogenated III-V Compounds

Evidence for hydrogen plasma neutralization of shallow donors in high purity (about 5 x 1014 cm-3) n-type GaAs epitaxial layers has been obtained by Pan et al. (1987a) from the observation of the discrete magneto-PTIS spectrum of the donors near 5 meV. This technique is very sensitive and it allowed to observe a decrease (between 10 and 50 percent) of the net 

FREQUENCIES (CM-1) OF THE VIBRATIONS OF X—H BONDS IN SOME SIMPLE MOLECULES (GAS PHASE UNLESS OTHERWISE SPECIFIED). THE r-F ACTOR IS THE RATIO OF THESE FREQUENCIES WITH THE CORRESPONDING ONES IN THE DEUTERATED MOLECULES. 

From a practical point of view, the optical detection of possible X—H bonds in hydrogenated samples is performed at LHeT as a better sensitivity is obtained at this temperature because the features are sharper than the ones observed at ambient. The sensitivity of Fourier Transform Spectroscopy (FTS) allows usually a normal incidence geometry of the optical beam. Two kinds of samples are generally used in the hydrogenation studies. The first are thin epitaxial layers (1 to 5 in thickness) with dopant concentrations in the 1017-102° at/cm3 range on a semi-insulating 

We will first describe the results obtained for n-type GaAs doped with silicon and then those on p-type GaAs and InP, trying to show how the spectroscopic results correlate with the electrical measurements to provide a consistent picture of the neutralization of dopants by hydrogen in III-V semiconductors. After considerations on the temperature dependence of the widths and positions of the H-related lines, we will discuss the occurrence and origin of other vibration lines associated also with hydrogen in as grown bulk and epitaxial III-V compounds. 

The first H-related line reported in hydrogen-treated doped GaAs was observed in GaAs Si. It was located at 896.82 cm-1 at LHeT and moved at 641.52 cm-1 in the D-treated sample (Jalil et at., 1987). The two lines were labelled 1-H and 1-D respectively. Fig. 12 shows line 1-H with the 

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