MOCVD Growth and Characterization of Be-Doped GaN

Abstract

Beryllium has been considered a potential alternative to magnesium as a p-type dopant in GaN, but attempts to produce conductive p-GaN:Be have not been successful. Photoluminescence studies have repeatedly shown Be to have an acceptor level shallower than that of Mg, but deep Be defects and other compensating defects render most GaN:Be materials n-type or semi-insulating at best. Previous reports use molecular beam epitaxy or ion implantation to dope GaN with Be, almost exclusively. Due to the high toxicity of Be organometallics, reports of GaN:Be by metal−organic chemical vapor deposition (MOCVD) have been largely absent. Here, we report a systematic study of growth of GaN:Be by MOCVD. All doped samples show the established UV band and yellow luminescence signature of GaN:Be, and growth conditions resulting in high-quality GaN with stable Be incorporation were established. Our results show that the MOCVD growth technique allows for Be incorporation pathways that have not been possible with previous growth methodologies and is highly promising in achieving p-type conductivity in GaN:Be.

Photoluminescence from Be‐Doped GaN Grown by Metal‐Organic Chemical Vapor Deposition

“…Other details about the growth can be found in ref. [19]. The concentrations of impurities from SIMS measurements for selected samples are given in Table 1, and the concentration–depth profiles of Be are shown in Figure 8 .…”

Photoluminescence from GaN Implanted with Be and F

“…The characteristic feature of the YL Be band is the two‐step quenching with increasing temperature. [ 2,3,29 ] This effect was observed in all samples without exception. Temperature dependences of the YL Be intensity for two representative samples (normalized at T = 18 K) are shown in Figure 3 .…”

“…The shape of the YL Be band can be fit using Equation (1) with the same parameters (Table 2) as for the YL Be band in Be-doped GaN grown by MBE, MOCVD, and in Be-implanted GaN. [2,3,18,29] The band maximum in semi-insulating GaN samples red-shifts by up to 60 meV with decreasing P exc from 0.1 to 10 À5 W cm À2 . As in the case of Ca-implanted GaN, [30] the shift can be caused by local electric fields in semi-insulating GaN.…”

“…This behavior indicates that the sample is semi-insulating. [28,29] 3.4.2. The UVL Be Band in Conductive n-type GaN…”

On the Origin of the Yellow Luminescence Band in GaN

“…[8] The distinguishing feature of the YL Be band is two-step quenching with increasing temperature. In n-type GaN samples, the first step is observed at T % 100 K, and the second quenching begins at T % 200 K. [8,113] In semi-insulating GaN:Be samples, the quenching occurs by an abrupt and tunable mechanism, and two steps are always observed. Beryllium is involved in the defect responsible for the YL Be band, yet its exact structure is not known.…”