Below-bandgap photoluminescence from GaAs substrates induced by pre-MBE-growth treatments

Abstract

We report the observation of below-GaAs-bandgap photoluminescence (PL) emission from semi-insulating GaAs substrates subjected to thermal annealing during the standard pre-MBE-growth processes. The below-GaAs-bandgap luminescence from defects were investigated using a combination of PL techniques including below-gap-excitation (BGE) and backside illuminated (BI) PL. Using BGE and BI PL, defects deep within the substrates were probed, and their spatial positions along the sample were analyzed. A PL peak at 1000 nm was observed after pre-bake annealing at 300°C, and further peaks at 905, 940 and 1150 nm were found after oxide desorption annealing at 600°C. These are attributed to the Ga-vacancy related defect, Ga-vacancy-complex defect, As-vacancy defect, and InGaAs states, respectively. This is the first report of the formation of such optically-active defects after annealing of GaAs at moderate temperature ranges (≤600°C), providing guidelines to distinguish desired electronic states for device applications from those that arise from defects which often confuse, and also degrade the device performances.

Photoluminescence of pre-growth treatment induced below-bandgap states in GaAs

“…GaAs, it was proposed that the deeper and larger excitation volume of BGE PL causes the increase in intensity. 12) For the n-GaAs in the present study, one of the main difference as compared with the s.i. GaAs in the previous study is the presence of significant free The observed peaks at 848, 926, and 1076 nm are attributed to the Si As , Si As -V As complex, and Si Ga -V Ga complex transitions, respectively.…”

“…This is in contrast with the case of s.i. GaAs substrate, 12) where increasing treatment tend to induce more defect and degrade the crystal. The difference in pregrowth treatment behavior between the n-GaAs and s.i.…”

“…The pre-growth treatment conditions are same as those in the previous study. 12) The standard pre-growth treatment involve the following subsequent steps: pre-baking at 300 °C for around 3 h, oxide desorption at 600 °C for 10 min, and growth of 100 nmundoped (u.d.) GaAs buffer layer at 590 °C for 15 min.…”

“…GaAs substrates. 12) The pre-growth treatments involve temperatures that are typical to molecular beam epitaxy (MBE) growth (⩽600 °C). Furthermore, the luminescence from the induced defects (between 0.9 and 1.3 μm) were found to significantly overlap with wavelengths used for GaAs-based optoelectronics, and hence could potentially impact or degrade device performance.…”

Below‐Bandgap Photoluminescence from GaAs

“…Some of the experimental results have been briefly discussed elsewhere . A typical AGE PL spectrum observed from the as‐supplied s.i.…”