Electron Mass in Dilute Nitrides and its Anomalous Dependence on Hydrostatic Pressure

The dependence of the electron mass on hydrostatic pressure $P$ in N-diluted ${\mathrm{GaAs}}_{1-x}{\mathrm{N}}_x$ ($x=0.10\%$ and 0.21%) is investigated by magnetophotoluminescence. Exceedingly large fluctuations (up to $60\%/\mathrm{kbar}$) in the electron mass with increasing $P$ are found. These originate from a pressure-driven tuning of the hybridization degree between the conduction band minimum and specific nitrogen-related states. Present results suggest a hierarchy between different nitrogen complexes as regards the extent of the perturbation these complexes exert on the electronic properties of the GaAs host.

Figure 1

(a) PL spectra at $T=90\mathrm{K}$ and $B=0\mathrm{T}$ of a ${\mathrm{GaAs}}_{1-x}{\mathrm{N}}_x$ sample with $x=0.10\%$ recorded at different hydrostatic pressures $P$. FE and $\mathrm{C}i$ indicate the free exciton and nitrogen complex-related recombinations, respectively. (b) Same as (a) but $x=0.21\%$.

Figure 2

(a) PL spectra at $T=90\mathrm{K}$ for different magnetic fields $B$ and two hydrostatic pressures on a ${\mathrm{GaAs}}_{1-x}{\mathrm{N}}_x$ sample ($x=0.10\%$). FE and $\mathrm{C}i$ indicate the free exciton and nitrogen complex-related recombinations, respectively. (b) Same as (a) but $x=0.21\%$. Notice that in both cases the spectral weight of NC states increases with $P$. (c) Dependence of the free-exciton diamagnetic shift (open symbols) $\Delta E_d$ on a magnetic field for different pressures in a ${\mathrm{GaAs}}_{1-x}{\mathrm{N}}_x$ sample with $x=0.10\%$. The dashed lines are a fit to the data by means of the model reported in Ref. 20. The exciton reduced mass is the only fitting parameter. (d) Same as (c) but $x=0.21\%$. $\Delta E_d$ data are vertically shifted for clarity purposes.

Figure 3

(a) Dependence of the electron effective mass at $T=90\mathrm{K}$ on hydrostatic pressure for a ${\mathrm{GaAs}}_{1-x}{\mathrm{N}}_x$ sample with $x=0.10\%$. (b) Same as (a) but $x=0.21\%$. (c) Free-exciton energy vs pressure (solid lines) at $T=90\mathrm{K}$ for the investigated samples. Symbols indicate the energy dependence on pressure of recombination bands related to N complexes in different samples (green ▵: $x=0.043\%$; blue ⋄: $x=0.10\%$; red □: $x=0.21\%$). Dashed lines are linear fits to the NC data. $\mathrm{C}i$ label complexes shown in Figs. 1, 2. $\mathrm{B}i$ label complexes not observed in the spectra shown in the previous figures. Open larger circles highlight pressure values related to a marked increase of the electron mass as shown in (a) and (b).