Electric- and magnetic-field effects on radiative recombination in modulation n-doped ZnSe/BeTe type-II quantum wells

Abstract

We have studied the photoluminescence properties of modulation n-doped ZnSe/BeTe/ZnSe type-II quantum wells. The luminescence spectra and the polarization anisotropy depend strikingly on both the n-doping into the barrier layers and an applied external electric field perpendicular to the layers. These are explained by screening of a built-in electric field with n-doping and Stark effects due to the applied electric field. We find optical Shubinkov-de Hass oscillations in both the photoluminescence intensity and the transition energy under a high magnetic field perpendicular to the well. These features and additional infrared cyclotron-resonance measurements demonstrate that two-dimensional electron gas of a high concentration has been formed in the doped samples. All these present the signature of the charged excitons and also of a correlated excitonic phase of type-II quantum wells.

Electron tunneling effects on radiative recombination in modulation n-doped ZnSe/BeTe type-II quantum wells

“…The PL spectra, the dashed and dotted lines, show the type-II transitions with a linear polarisation along the [110] and [1 10] axes, respectively. As reported in our previous work [15,19] the two separated macro PL peaks L and H of the undoped sample in Fig. 2(a) correspond to the type-II transitions of different interfaces since the two peaks have opposite linear polarisation, and the energy interval ∆E of 30 meV of the two peaks originates from a strong Stark effects induced by a built-in electric field F .…”

“…The QWs in the samples consisted of one set (for #237), and three sets (for #288) of symmetrical ZnSe (28 ML) /BeTe (10 ML)/ZnSe (28 ML) layers as described in detail in Refs. [15], [18] and [19], where 1 ML was approximately equal to 0.28 nm. In the n-doped sample, the doped layers (ZnCl 2 ) were separated from the QWs by 10 nm-thick barrier layers as shown in Fig.…”

“…Other parameters of the two samples were identical. [15,18,19] The samples were grown in Ultrafast Photonic Devices Laboratory of AIST in Japan.…”

Spatially separated indirect photoemission in undoped ZnSe/BeTe type-II quantum wells studied in pulse magnetic fields

“…Optical properties of the SID PL in the modulation ndoped samples of the same quantum wells were investigated in our previous paper and a negatively charged exciton-type transition as well as a cyclotron resonance of conduction electrons in the ZnSe layer was reported [4]. Stable existence of trions with a type-II alignment was also predicted by theories [5].…”

Type-I interband transition in undoped ZnSe/BeTe type-II quantum wells under high excitation density

“…The ZnSe/BeTe quantum well structures have a type-II band alignment with large band offsets, namely 2.3 eV for the conduction band and 0.9 eV for the valence band [8][9][10]. In such deep potential wells, photo-excitation in ZnSe layers causes a unique situation where the electrons stay in the same layer, whereas some of the holes escape from the ZnSe layer, and are injected into the next neighbor BeTe layer due to the energy minima for electrons and holes lying in different layers [11][12][13][14][15].…”