SEMICONDUCTOR DEVICE PHYSICS AND DESIGN

78 CHAPTER 2. ELECTRONIC LEVELS IN SEMICONDUCTORS

E 2

Ec (bulk)

–W/ 2 0 +W/ 2

z

E 1

E 2

E 1

k 11

E = h^2 k// + E 2

2 m*

Energy

P arabol i c two- di mensi onal subbands

ΔEc

E = h^2 k// + E 1

2m*

E 1 (HH)

E 1 (L H)

E 2 (HH)

E 2 (L H)

L i ght hol e

subbands

Heavy hole

subbands

Valence

band

C onducti on

band

Ev (bulk)

Density of states

E ffective gap

Well gap

Q uantum wel l E vs k 11

2

2

Figure 2.33: Schematic of density of states in a 3–, 2– and 1–dimensional system. The subband
structure is shown.