Beryllium alkyls
Beryllium alkyls such as dimethylberyllium BeMe2 or diethylberyllium BeEt2, have been applied as precursor for MOVPE of beryllium-contaning GaAs, AlGaAs, InGaAs layers; with advantage of Be as p-dopant is significantly lower memory effects and lower diffusion rate compared to Zn and Mg. High p-doping levels up over 7x1019 cm-3 have been achieved (f.e using BeEt2 as dopant), showing that beryllium alkyls are promising p-type dopants for MOCVD applications.
Dimethylberyllium BeMe2
Dimethylberyllium for ALD of BeO
Dimethylberyllium BeMe2 has been applied as a precursor for the ALD growth of beryllium oxide BeO thin films (5-10 nm) on Si and GaAs substrates at 200 °C using a Nano Cambridge ALD module, with water H2O as the second reagent. Electrical and physical properties of the grown layers were evaluated as a barrier/passivation layer in the III-V devices.
BeO ALD-grown layers exhibited lower interface defect density/ lower hysteresis, smaller frequency dispersion and lower leakage current density at the same effective oxide thickness, as well as significant self-cleaning effect, compared to Al2O3 layers. These properties combined with high thermal stability, large energy band-gap(10.6 eV), effective diffusion barrier, and low intrinsic structural defects, make ALD –grown BeO an excellent candidate for the interfacial passivation layer applications in the channel III-V devices. [[i]
Diethylberyllium BeEt2
Diethylberyllium [BeEt2]2
Diethylberylluum BeEt2 (DEBe), or more correctly dimer [BeEt2]2 , has been reported to be applied as a p-dopant precursor for the growth of heavily beryllium-doped (In,Ga)As by MOVPE. No memory effects were observed, and hole concentrations from 1015 to 1020 cm-3 could be obtained reproducibly.
Dependence of electrical characteristics of Be-doped layers on DEBe flow rate, substrate temperature, GaAs growth rate, and As: Ga molar flow ratio were studied.. The activation energy of Be in GaAs was determined by Hall effect measurements as a function of temperature. SIMS was used to identify the principal contaminants in the DEBe, as well as to check abruptness of high to low p-doping transitions. [i]
[i]J. D. Parsons, L. S. Lichtmann, F. G. Krajenbrink, D. W. Brown
Journal of Crystal Growth, Volume 77, Issues 1-3, September 1986, Pages 32-36,
MOVPE growth of beryllium-doped gallium arsenide using diethylberyllium
BeEt2 for Be-doped AlGaAs
Diethylberyllium has been applied for modulation Be-doping during OMVPE of p-type AlGaAs thin layers; the dependence of free carrier concentration vs Al% for AlxGa1−xAsx (x = 0–0.5) was studied. For x = 0–0.43, a free carrier concentration greater than 1 × 1018 cm−3 was achieved with no carrier freeze-out down to 77 K. In the Al0.43Ga0.57As(Be)/GaAs heterostructures exhibiting a two-dimensional hole gas (2DHG) effect, for a sheet carrier density of about 4.5 × 1011 cm−2, hole mobilities of 394, 3750, and 21200 cm2/Vs (at 300, 77, 4 K, respectively) were determined by Hall or cyclotron resonance measurements.[[i] ]
BeEt2 for Be-doped InGaAs MOCVD
Diethylberyllium has been applied as p-dopant for the growth of heavily p-doped InGaAs films lattice matched to InP by conventional low-pressure MOCVD at temperatures 500-600°C. Doping level (>1019 cm-3) was independent of growth temperature in this range. Be concentration in InGaAs was found to be proportional to the second power of BeEt2 flow rate. Based on thermodynamic analysis, it was suggested that Be is incorporated through the β-elimination decomposition of a diethylberyllium dimer. The doping efficiency using BeEt2 is at least an order magnitude larger than that for a Zn dopant. [[i]
Another study of Be-doping of InGaAs by MOCVD reported possibility to reach hole concentration level up to 7.7× 1019 cm−3 using BeEt2 as dopant precursor at growth temperature 500°C (one of highest p-doping level reported for InGaAs material system). Significant incorporation of oxygen in grown layers was determined by SIMS. Using Be-doped InGaAs as the base layer, InP-based heterostructure bipolar transistors have been prepared. [ii]
[i]Takashi Kobayashi, Kenji Kurishima and Tadao Ishibashi
Journal of Crystal Growth, Volume 142, Issues 1-2, 1 September 1994, Pages 1-4
Beryllium-doped InGaAs grown by low-pressure metalorganic chemical vapor deposition
[ii]B. T. McDermott, C. W. Seabury, C. W. Farley and J. A. Higgins, Journal of Electronic Materials , 1993, Volume 22, Number 5, 555-558, DOI: 10.1007/BF02661630; Highly doped GalnAs using diethylberyllium by MOCVD for InP-based heterostructure bipolar transistor applications
[i]R. S. Sillmon, S. M. Hues, D. K. Gaskill, N. Bottka and P. E. Thompson
Journal of Electronic Materials, Volume 18, Number 4, 501-504, DOI: 10.1007/BF02657779
“OMVPE growth of p-AlGaAs/GaAs heterojunctions using diethylberyllium”
Share this page